Diagnosis and Differential Diagnosis of Rheumatoid Arthritis - UpToDate
Diagnosis and Differential Diagnosis of Rheumatoid Arthritis - UpToDate
Diagnosis and Differential Diagnosis of Rheumatoid Arthritis - UpToDate
Authors: PJW Venables, MA, MB BChir, MD, FRCP, Ravinder N Maini, BA, MB BChir, FRCP, FMedSci, FRS
Section Editor: James R O'Dell, MD
Deputy Editor: Paul L Romain, MD
All topics are updated as new evidence becomes available and our peer review process is complete.
Literature review current through: Jul 2017. | This topic last updated: Jan 22, 2016.
Early recognition and treatment with disease-modifying antirheumatic drugs (DMARDs) is important in
achieving control of disease and prevention of joint injury and disability. However, in patients with early
disease, the joint manifestations are often difficult to distinguish from other forms of inflammatory polyarthritis.
The more distinctive signs of RA, such as joint erosions, rheumatoid nodules, and other extraarticular
manifestations, are seen primarily in patients with longstanding, poorly controlled disease but are frequently
absent on initial presentation.
This topic will review the approach to the diagnosis and differential diagnosis of RA. The clinical features of
this disorder, its extraarticular manifestations, and laboratory markers that are clinically useful in the
diagnosis of RA are discussed in detail separately. (See "Clinical manifestations of rheumatoid arthritis" and
"Overview of the systemic and nonarticular manifestations of rheumatoid arthritis" and "Biologic markers in
the diagnosis and assessment of rheumatoid arthritis".)
EVALUATION FOR SUSPECTED RA — Rheumatoid arthritis (RA) should be suspected in the adult patient
who presents with inflammatory polyarthritis. The initial evaluation of such patients requires a careful history
and physical examination, along with selected laboratory testing to identify features that are characteristic of
RA or that suggest an alternative diagnosis. (See "Clinical manifestations of rheumatoid arthritis" and
'Differential diagnosis' below.)
● We perform a thorough medical history, with particular attention to joint pain, reported swelling, and the
presence, location (peripheral joints rather than low back), and duration (at least 30 minutes) of morning
stiffness. The absence of other conditions or symptoms suggesting an alternative diagnosis, such as
psoriasis, inflammatory bowel disease (IBD), or a systemic rheumatic disease such as systemic lupus
erythematosus (SLE), helps to exclude other disorders.
Symptoms of arthritis that have been present for a short time (for example, less than six weeks) may well
be due to an acute viral polyarthritis rather than to RA. The longer symptoms persist, the more likely the
diagnosis of RA becomes. Thus, in patients presenting very early, close observation with frequent follow-
up appointments is required, with repeated serologic analysis for anti-cyclic citrullinated peptide (CCP)
antibodies, rheumatoid factor (RF), and acute phase reactants. In a minority of patients, several such
visits are required before the differential diagnosis between RA and viral arthritis becomes established.
(See "Clinical manifestations of rheumatoid arthritis", section on 'Typical "classic" RA' and 'Differential
diagnosis' below.)
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● A complete physical examination is indicated to assess for synovitis, including the presence and
distribution of swollen or tender joints and limited joint motion; extraarticular disease manifestations,
such as rheumatoid nodules; and signs of diseases, such as SLE or psoriasis, included in the differential
diagnosis. (See "Clinical manifestations of rheumatoid arthritis", section on 'Symptoms and physical
findings' and "Rheumatoid nodules" and 'Differential diagnosis' below.)
● We perform the following laboratory tests, which support the diagnosis if positive and/or elevated:
• RF and anti-CCP antibodies – We perform both RF and anti-CCP antibody testing when initially
evaluating a patient with suspected RA. The results of both tests are informative, since a positive
result for either test increases overall diagnostic sensitivity, while the specificity is increased when
both tests are positive. Despite this, both tests are negative on presentation in up to 50 percent of
patients and remain negative during follow-up in 20 percent of patients with RA. (See "Biologic
markers in the diagnosis and assessment of rheumatoid arthritis", section on 'Rheumatoid factors'
and "Biologic markers in the diagnosis and assessment of rheumatoid arthritis", section on 'Anti-
citrullinated peptide antibodies'.)
• Erythrocyte sedimentation rate (ESR) and serum C-reactive protein (CRP) levels – Both the ESR
and CRP are typically elevated in RA. (See "Biologic markers in the diagnosis and assessment of
rheumatoid arthritis", section on 'Erythrocyte sedimentation rate' and "Biologic markers in the
diagnosis and assessment of rheumatoid arthritis", section on 'C-reactive protein'.)
● We perform the following testing in all patients, which may be helpful in the differential diagnosis of RA
and as baseline testing for monitoring of disease activity or progression and medication safety:
• Antinuclear antibody (ANA) testing – A negative ANA helps exclude SLE and other systemic
rheumatic diseases; the ANA may be positive in up to one-third of patients with RA. In patients with
a positive ANA, anti-double stranded DNA and anti-Smith antibody testing should also be
performed; these antibodies have high specificity for SLE. (See "Measurement and clinical
significance of antinuclear antibodies".)
• Complete blood count (CBC) with differential and platelet count, tests of liver and kidney function,
serum uric acid, and a urinalysis – The CBC is often abnormal in RA, with anemia and
thrombocytosis consistent with chronic inflammation. Liver and kidney testing abnormalities indicate
a disorder other than RA; if caused by comorbid conditions, they may affect therapeutic choices or
drug dosing. Hyperuricemia may prompt additional efforts, including arthrocentesis and crystal
search, to exclude gout; polyarticular gout can infrequently be mistaken for RA. (See "Hematologic
manifestations of rheumatoid arthritis", section on 'Anemia of chronic disease' and "Hematologic
manifestations of rheumatoid arthritis", section on 'Platelet abnormalities' and 'Differential diagnosis'
below.)
• Radiographs of the hands, wrists, and feet – We obtain radiographs during the initial evaluation
primarily as a baseline for monitoring disease progression. However, characteristic joint erosions
may be observed in patients presenting with symptoms for the first time and, hence, aid in
diagnosis. Additionally, in patients with other disorders, such as psoriatic arthritis,
spondyloarthropathy, gout, or chondrocalcinosis, radiographic changes more characteristic of these
conditions may point to an alternative diagnosis. (See '2010 ACR/EULAR criteria' below and
'Differential diagnosis' below and "Clinical manifestations of rheumatoid arthritis", section on
'Imaging'.)
• Serologic studies for infection – In patients with a very short history (for example, less than six
weeks) particularly those who are seronegative for anti-CCP and RF, we perform serologic testing
for human parvovirus B19, hepatitis B virus (HBV), and hepatitis C virus (HCV). In areas endemic
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for Lyme disease, we perform serologic studies for Borrelia as well. (See 'Viral polyarthritis' below
and "Specific viruses that cause arthritis" and "Diagnosis of Lyme disease", section on 'Indications
for serologic testing'.)
• Synovial fluid analysis – We perform arthrocentesis and synovial fluid analysis for the diagnosis or
exclusion of gout, pseudogout, or an infectious arthritis if a joint effusion is present and if there is
uncertainty regarding the diagnosis, particularly in the setting a monoarthritis, oligoarthritis, or
asymmetric joint inflammation. Synovial fluid testing should include a cell count and differential,
crystal search, and Gram stain and culture. Synovial fluid analysis should also be obtained to
exclude infection or crystalline arthropathy in patients who undergo glucocorticoid injections for
symptomatic relief. (See "Clinical manifestations of rheumatoid arthritis", section on 'Laboratory
findings' and "Synovial fluid analysis".)
• Magnetic resonance imaging (MRI) and ultrasound – MRI studies and ultrasonography do not have
an established role in the routine evaluation of patients with polyarthritis. However, MRI and
ultrasound are more sensitive than radiography at detecting changes resulting from synovitis and
may be helpful in establishing the presence of synovitis in patients with normal radiographs and
uncertainty regarding either the diagnosis or the presence of inflammatory changes, such as
patients with obesity or subtle findings on examination. (See "Clinical manifestations of rheumatoid
arthritis", section on 'Imaging'.)
DIAGNOSIS
Our diagnostic criteria — The diagnosis of rheumatoid arthritis (RA) can be made when the following
clinical features are all present:
● Inflammatory arthritis involving three or more joints. (See "Clinical manifestations of rheumatoid arthritis",
section on 'Symptoms and physical findings'.)
● Positive rheumatoid factor (RF) and/or anti-citrullinated peptide/protein antibody (such as anti-cyclic
citrullinated peptide [CCP])) testing. (See "Biologic markers in the diagnosis and assessment of
rheumatoid arthritis", section on 'Anti-citrullinated peptide antibodies'.)
● Elevated levels of C-reactive protein (CRP) or the erythrocyte sedimentation rate (ESR). (See "Biologic
markers in the diagnosis and assessment of rheumatoid arthritis", section on 'Erythrocyte sedimentation
rate'.)
● Diseases with similar clinical features have been excluded, particularly psoriatic arthritis, acute viral
polyarthritis, polyarticular gout or calcium pyrophosphate deposition disease, and systemic lupus
erythematosus (SLE). (See 'Differential diagnosis' below.)
These criteria are consistent with the 2010 American College of Rheumatology (ACR)/European League
Against Rheumatism (EULAR) classification criteria for RA. (See '2010 ACR/EULAR criteria' below.)
The diagnosis of RA may also be made in some patients who do not meet all of our criteria. (See 'Patients
not meeting above criteria' below.)
Inflammatory arthritis — Arthritis is typically present in the metacarpophalangeal (MCP) and proximal
interphalangeal (PIP) joints of the hands. The wrists are also commonly involved, as are the
metatarsophalangeal (MTP) joints in the feet, but any upper or lower extremity joint may be affected.
Symmetric polyarthritis, particularly of the MCP, MTP, and/or PIP joints, strongly suggests RA. Although distal
interphalangeal (DIP) joint disease can occur in patients with RA, DIP involvement strongly suggests a
diagnosis of osteoarthritis or psoriatic arthritis. (See "Clinical manifestations of rheumatoid arthritis", section
on 'Symptoms and physical findings' and 'Osteoarthritis' below and 'Psoriatic arthritis' below.)
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Serology — RFs occur in 70 to 80 percent of patients with RA. Their diagnostic utility is limited by their
relatively poor specificity, since they are found in 5 to 10 percent of healthy individuals, 20 to 30 percent of
people with SLE, virtually all patients with mixed cryoglobulinemia (usually caused by hepatitis C virus [HCV]
infections), and in those with many other inflammatory conditions. Higher titers of RF (at least three times the
upper limit of normal) have somewhat greater specificity for RA. The prevalence of RF positivity in healthy
individuals rises with age. (See "Origin and utility of measurement of rheumatoid factors" and "Biologic
markers in the diagnosis and assessment of rheumatoid arthritis", section on 'Rheumatoid factors'.)
Acute phase reactants — Elevations of the ESR and/or CRP level are consistent with the presence of an
inflammatory state, such as RA. Normal acute phase reactants may occur in untreated patients with RA, but
such findings are very infrequent. The degree of elevation of these acute phase reactants varies with the
severity of inflammation. As an example, an ESR of 50 to 80 is not uncommon in patients with severely active
RA. By comparison, an ESR of 20 to 30 can be observed with only a few mildly to moderately active joints.
Although increased levels of acute phase reactants are not specific for RA, they are often useful for
distinguishing inflammatory conditions from noninflammatory disorders that present with musculoskeletal
symptoms (eg, osteoarthritis or fibromyalgia). (See "Acute phase reactants" and "Biologic markers in the
diagnosis and assessment of rheumatoid arthritis", section on 'Erythrocyte sedimentation rate' and "Biologic
markers in the diagnosis and assessment of rheumatoid arthritis", section on 'C-reactive protein'.)
Patients not meeting above criteria — The diagnosis of RA may also be made in patients without all the
criteria described in the previous section. Examples include the following:
● Seronegative RA – Patients who lack both RF and anti-CCP antibodies may be diagnosed with RA
based upon findings otherwise characteristic of RA if appropriate exclusions have been met. Such
patients with seronegative RA differ from anti-CCP-positive patients genetically and in their
environmental risks, disease severity, and clinical responsiveness to some medications [6]. Additional
research is needed to better characterize this population.
● Recent onset RA – Patients with disease for less than six weeks may be diagnosed with RA based
upon findings otherwise characteristic of RA, including anti-CCP antibodies, if testing for viral serologies
is negative and if other appropriate exclusions have been met. (See 'Evaluation for suspected RA' above
and 'Viral polyarthritis' below.)
● Inactive RA – Patients without active arthritis or elevated acute phase reactants (eg, due to treatment of
recent onset disease or with longstanding disease) may be diagnosed with RA based upon well-
documented past findings characteristic of RA, especially in the presence of positive testing for RF and
anti-CCP, or typical bone erosions on radiography, and in the absence of an alternative more likely
diagnosis.
Patients in the several categories above, and other patients who should be diagnosed with RA but do not
meet our standard criteria, will generally have findings that are consistent with the 2010 ACR/EULAR
classification criteria for RA [7,8]. These criteria were developed for the classification of patients with RA for
the purpose of epidemiologic studies and clinical trials, not primarily for clinical diagnosis. Nevertheless, the
same features that are of value in classification tend to be useful for the purpose of diagnosis in clinical
practice. Further study is required to establish their utility as diagnostic criteria in general practice. (See
'Classification criteria' below.)
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2010 ACR/EULAR criteria — Using the 2010 ACR/EULAR classification criteria for RA, classification as
definite RA is based upon the presence of synovitis in at least one joint, the absence of an alternative
diagnosis that better explains the synovitis, and the achievement of a total score of at least 6 (of a possible
10) from the individual scores in four domains [7,8,11]. The highest score achieved in a given domain is used
for this calculation. These domains and their values are:
• 2 to 10 large joints (from among shoulders, elbows, hips, knees, and ankles) = 1 point
• 1 to 3 small joints (from among the metacarpophalangeal joints, proximal interphalangeal joints,
second through fifth metatarsophalangeal joints, thumb interphalangeal joints, and wrists) = 2 points
● Elevated acute phase response (erythrocyte sedimentation rate [ESR] or C-reactive protein [CRP])
above the ULN = 1 point
In addition to those with the criteria above, which are best suited to patients with newly presenting disease,
the following patients are classified as having RA:
● Patients with erosive disease typical of RA with a history compatible with prior fulfillment of the criteria
above
● Patients with longstanding disease, including those whose disease is inactive (with or without treatment)
who have previously fulfilled the criteria above based upon retrospectively available data
1987 ACR criteria — It is important to recognize that RA has been defined in virtually all clinical trials of
drugs for RA initiated from 1987 through 2010 based upon the criteria developed and validated by the ACR
(previously the American Rheumatism Association) in 1987 (table 1) [9,10]. A patient was classified as
having RA if at least four of these seven criteria were satisfied; four of the criteria must have been present for
at least six weeks: morning stiffness, arthritis of three or more joint areas, arthritis of the hands, and
symmetric arthritis. Rheumatoid factor (RF) was included as a criterion, but anti-cyclic citrullinated peptide
(CCP) antibody testing was not available at that time. The other two criteria were rheumatoid nodules and
radiographic erosive changes typical of RA, but these are generally not present in the early stages of
disease.
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Thus, while these criteria were very good at separating inflammatory from noninflammatory arthritis, the
major drawback of the 1987 criteria has been their insensitivity in identifying some patients with early disease
who subsequently develop typical established RA [10]. On the other hand, the criteria did not require any
exclusions, and patients could initially fulfill the diagnostic criteria but occasionally evolve into other
diagnoses, particularly systemic lupus erythematosus (SLE), Sjögren's syndrome, scleroderma, mixed
connective tissue disease, psoriatic arthritis, and crystalline arthritis.
Viral polyarthritis — A number of viral infections may cause an acute viral polyarthritis.
● Viral infections such as rubella [12], parvovirus B19 [13], and hepatitis B virus (HBV) can cause an acute
polyarthritis syndrome that may be mistaken for the inflammatory polyarthritis of RA. However, the
syndrome is usually short-lived, lasting only from a few days to several weeks, and rarely beyond six
weeks. Hepatitis C virus (HCV) can cause a polyarthritis or oligoarthritis in a minority of patients, but is
more commonly associated with arthralgias.
Serologic testing can help identify patients with HBV, HCV, or human parvovirus B19 in some individuals
with early disease, but a viral etiology cannot always be excluded until after symptoms are present for at
least six to eight weeks in the absence of diagnostic serologic testing for a specific virus (see "Specific
viruses that cause arthritis") Unlike rheumatoid factor (RF) (which may occur in patients with a variety of
infections, including HCV infection), anti-cyclic citrullinated peptide (CCP) antibodies are usually negative
in patients with HCV infection who do not have RA. (See "Biologic markers in the diagnosis and
assessment of rheumatoid arthritis", section on 'Anti-citrullinated peptide antibodies'.)
● Increasingly reported in travelers, alphaviruses are globally distributed mosquito-borne RNA viruses that
cause epidemics of polyarthritis/arthralgia [14,15]. Among all of the viruses that can cause arthritis, the
alphaviruses are unusual because nearly all symptomatic infections in adults result in joint symptoms.
The incubation period lasts from several days to three weeks; infection is typically associated with triad
of fever, arthritis, and rash [14]. However, all aspects of the triad may not be present, thereby making the
diagnosis difficult.
One such alphavirus, Chikungunya, has become a global disease with increasing world travel and has
caused large outbreaks in Italy, India, Indian Ocean islands, and in the Caribbean region and
surrounding countries [16,17]. Patients with more persistent disease can mimic seronegative RA
clinically to a sufficient degree to satisfy the 2010 classification criteria for RA if the initial symptoms of
fever and rash and history of travel to an endemic region are not appreciated [18]. Serologic studies can
help to document exposure to the Chikungunya virus. (See "Chikungunya fever", section on 'Clinical
manifestations'.)
Alphavirus infections generally resolve over three to six months. The diagnosis of alphavirus infection
can be made by appropriate serologic testing in travelers from endemic areas with persistent arthritic
symptoms. (See "Specific viruses that cause arthritis", section on 'Alphaviruses' and "Chikungunya
fever".)
● A large joint arthritis has been reported in association with human T lymphotropic virus type 1 (HTLV-I)
[19]. These infections are sometimes associated with the presence of RFs (usually in low titer),
antinuclear antibodies (ANA), and elevated acute phase reactants. HTLV-I infections can generally be
distinguished from RA by the finding of specific antiviral antibodies and the typically self-limited nature of
arthritis associated with HTLV-I.
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Systemic rheumatic diseases — Early RA may be difficult to distinguish from the arthritis of systemic lupus
erythematosus (SLE), Sjögren's syndrome, dermatomyositis (DM), or overlap syndromes such as mixed
connective tissue disease. In contrast with RA, these disorders are generally characterized by the presence
of other systemic features, such as rashes, dry mouth and dry eyes, myositis, or nephritis, and by various
autoantibodies not seen in RA. Additionally, the relative responses of the erythrocyte sedimentation rate
(ESR) and C-reactive protein (CRP) can be less well-correlated with each other in other diseases, particularly
SLE, than in RA. Whereas both are commonly raised in RA, the CRP is often normal or only minimally
elevated in patients with active SLE even when the ESR is elevated.
Taken together, the pattern of longstanding disease, morning stiffness, symmetric arthritis, subcutaneous
nodules, and the deformities characteristic of RA does not develop in these other disorders. There are
several exceptions to this observation:
● Morning stiffness is common in all inflammatory arthritides. Symmetric arthritis is seen in patients with
SLE and can be present in other disorders. Infrequently, nodules similar to those seen in RA may occur
in patients with SLE, and other nodular lesions may mimic rheumatoid nodules. (See "Rheumatoid
nodules", section on 'Subcutaneous nodules' and "Rheumatoid nodules", section on 'Differential
diagnosis'.)
● An erosive arthritis has been described in some overlap syndromes, particularly those associated with
anti-tRNA synthetases and anti-U1 RNP antibodies [20]. (See "Clinical manifestations of mixed
connective tissue disease".)
● Jaccoud's arthropathy occurs in up to 5 to 10 percent of patients with Sjögren's syndrome or SLE and
can also occur in sarcoidosis [21]. (See "Musculoskeletal manifestations of systemic lupus
erythematosus" and "Sarcoid arthropathy".)
The joint deformities of Jaccoud's arthropathy are not caused by destruction of joints but by loosening
and lengthening of periarticular structures and tendons. The ulnar drift or swan neck deformities caused
by this disorder resemble RA superficially but can be distinguished by the fact that they are "correctable"
on physical examination: fingers with these deformities can be moved manually back into normal
alignment. In addition, radiographs in Jaccoud's arthropathy rarely reveal the cartilage loss, erosions, or
cysts that are typical of longstanding RA.
Hypermobility syndrome and fibromyalgia — Pain, rather than stiffness or swelling, is the dominant
symptom of the two common disorders, hypermobility syndrome and fibromyalgia [26,27]. Although the
hypermobility syndrome and fibromyalgia can both bear superficial resemblances to RA due to the presence
of polyarthralgia, there are important distinguishing features:
● The hypermobility syndrome is associated with hyperextensible joints, and patients lack signs of
synovitis. (See "Joint hypermobility syndrome".)
● Fibromyalgia is associated with tender points at nonarticular sites such as at the medial portions of the
elbows, across the trapezius muscle, and down the spine; there is no evidence of synovitis on
examination, such as swelling, warmth, or diminished joint range of motion, although patients may
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exhibit joint line tenderness on exam. (See "Clinical manifestations and diagnosis of fibromyalgia in
adults".)
● Neither the hypermobility syndrome nor fibromyalgia is associated with significant titers of RF or anti-
CCP antibodies or with elevated levels of acute phase reactants.
Although RA is normally not difficult to distinguish from fibromyalgia, a significant minority of patients with RA
also develop fibromyalgia. The source of complaints in such patients needs to be carefully assessed to
distinguish heightened pain sensitivity from pain related to inflammatory joint disease.
Reactive arthritis and arthritis of IBD — Reactive arthritis often presents as a monoarthritis or oligoarthritis
in large joints, such as the knees, and RA may occasionally present in this fashion as well [28]. The physical
signs of both reactive arthritis and RA can be identical in the knees. (See "Reactive arthritis".)
The following findings on history, physical examination, or other assessments are more consistent with
reactive arthritis than RA:
Involvement of the hands in reactive arthritis does not pose as great a diagnostic dilemma as that of the
knees. Hand arthritis is more commonly asymmetric than in RA. Furthermore, reactive arthritis will often
involve not only the joint but also the tenosynovium, entheses, and surrounding tissues of the digit, giving rise
to a characteristic "sausage" swelling of the fingers (or toes if the feet are involved) (picture 1).
The arthritis associated with inflammatory bowel disease (IBD) or other gastrointestinal (GI) disorders is also
part of the differential diagnosis. Patients with IBD may develop a peripheral polyarthritis with prominent
involvement of the metacarpophalangeal (MCP) joints that can be mistaken for RA; other presentations
include predominantly large joint oligoarticular involvement or a spondyloarthropathy with sacroiliitis. This
disorder may be missed if abdominal symptoms or symptoms of diarrhea and/or blood or mucus in the stool
are not prominent or are not specifically sought in the history. (See "Clinical manifestations and diagnosis of
arthritis associated with inflammatory bowel disease and other gastrointestinal diseases".)
Lyme arthritis — Lyme arthritis, a late manifestation of Lyme disease, occurs primarily in individuals who live
in or travel to Lyme disease-endemic areas. Lyme arthritis is characterized by intermittent or persistent
inflammatory arthritis in a few large joints, especially the knee. The most commonly involved joints, after the
knee, are the shoulder, ankle, elbow, temporomandibular joint, and wrist. Migratory arthralgias without frank
arthritis may occur during early localized or early disseminated Lyme disease. (See "Musculoskeletal
manifestations of Lyme disease".)
The diagnosis of Lyme arthritis can usually be made by serologic testing, which should be performed in
patients presenting with undiagnosed inflammatory arthritis in endemic areas. In addition, several clinical
features help distinguish Lyme arthritis from RA. Unlike RA, for example, involvement of the small joints of
the hands and feet is uncommon in patients with Lyme arthritis. Furthermore, many, but not all, patients with
Lyme arthritis will describe an antecedent history of erythema migrans or other early disease manifestations.
(See "Musculoskeletal manifestations of Lyme disease", section on 'Laboratory testing'.)
Psoriatic arthritis — Psoriatic arthritis can be difficult to distinguish from RA because a symmetric
polyarthritis can be observed in both disorders [29]. We generally make the diagnosis of psoriatic arthritis in
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such patients who also have psoriasis and are seronegative for RF and anti-CCP. However, we diagnose RA
in those with a symmetric polyarthritis who are seropositive for at least one of these antibodies, since skin
psoriasis is so common. However, serologic testing and skin findings may not be informative, since patients
with RA may not have RF or CCP antibodies (eg, seronegative RA) and the joint symptoms of psoriatic
arthritis may precede the onset of skin disease by many years. Such patients should be evaluated and
monitored for other signs more characteristic of psoriatic arthritis, such as nail changes or enthesitis;
occasional patients exhibit overlapping features of both disorders.
In some patients with a symmetric inflammatory polyarthritis, the only clue to the diagnosis of psoriatic
arthritis is a family history of psoriasis. However, in the majority, the findings of skin psoriasis, nail changes
(onychodystrophy), sausage toes or fingers, oligoarticular asymmetric large joint or spinal involvement,
and/or arthritis mutilans help distinguish the two entities. (See "Clinical manifestations and diagnosis of
psoriatic arthritis".)
Polymyalgia rheumatica — Polymyalgia rheumatica (PMR) can sometimes be mistaken for RA in patients
presenting with more limited arthritis over the age of 50 who are seronegative or only have a low RF titer.
Unlike RA, PMR is usually associated with marked myalgias in the shoulders and hips, and joint involvement
tends to be milder, more limited, and more often asymmetric.
Stiffness is thus more axial in PMR and more likely to be described as difficulty getting out of bed, while
stiffness in the small joints of the hands and other involved joints predominates in RA, in which difficulty
buttoning clothing is more likely to be reported. However, similar complaints to RA may be present in patients
with PMR with synovitis affecting the small joints in the hands.
The arthritis in PMR tends to respond strikingly to modest doses of glucocorticoids used to control other
symptoms [30]. In patients initially diagnosed with PMR, persistent or recurrent small joint arthritis with
tapering of glucocorticoids and the absence of other findings suggestive of PMR may lead to a change in the
diagnosis to RA after several months or even years of treatment. (See "Clinical manifestations and diagnosis
of polymyalgia rheumatica".)
Crystalline arthritis — Crystalline arthritis (gout and pseudogout) can become chronic and even assume a
polyarticular distribution. The diagnosis is established by the finding of urate or calcium pyrophosphate
crystals, respectively, in synovial fluids. The presence of tophi on physical examination, the detection of
serological markers of RA, and the characteristic appearance of gouty erosions are also useful in
distinguishing RA from polyarticular gout. (See "Clinical manifestations and diagnosis of gout" and "Clinical
manifestations and diagnosis of calcium pyrophosphate crystal deposition (CPPD) disease".)
Infectious arthritis — Infectious arthritis is usually monoarticular, but polyarthritis can occur. The diagnosis
is established by culturing the pathogen from the synovial fluid or from the blood. Patients with septic arthritis
may or may not appear toxic on examination, depending upon the stage of their infection, the presence of
medications that can mask infection (eg, glucocorticoids), and other clinical variables. Peripheral blood
leukocytosis with a left shift is common but not invariably present.
A low threshold for suspecting infection is required, particularly in compromised hosts. Patients with RA are
at increased risk for joint infections because a damaged joint can serve as a nidus of infection. Synovial fluid
changes, including marked granulocytosis and low glucose levels, are similar to those seen in RA. (See
"Septic arthritis in adults".)
Osteoarthritis — Osteoarthritis (OA) can be confused with RA in the middle aged or older patient when the
small joints of the hands are involved. However, different patterns of clinical involvement usually permit the
correct diagnosis (table 3). The following are examples (see "Clinical manifestations and diagnosis of
osteoarthritis"):
● OA of the fingers typically affects the distal interphalangeal joints and is frequently associated with
Heberden's nodes in this area. In contrast, RA typically affects the MCP and proximal interphalangeal
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● Swelling of the joints is hard and bony in OA. In contrast, soft, warm, boggy, and tender joints are typical
of RA.
● Stiffness of the joint is a very common feature of RA but is relatively uncommon in OA. Furthermore, the
stiffness of RA is characteristically worse after resting the joint (eg, morning stiffness), while the stiffness
of OA, if present, is typically worse after any effort and is often described as evening stiffness. Morning
stiffness in OA, when present, is usually transient or lasts no more than a few minutes, unlike the more
sustained stiffness typical of RA.
● Radiographs also help distinguish RA from OA. OA is characterized by narrowing of the joint space due
to cartilage loss and osteophytes due to bone remodeling, but not erosions or cysts.
● OA is classically associated with the absence of RFs and normal levels of acute phase reactants.
However, RFs may be present, usually in low titer, consistent with the patient's (older) age.
Paraneoplastic disease — Joint pain or frank polyarthritis can occur in association with cancer. The
following are some examples:
Sarcoid arthropathy — Chronic arthritis in sarcoidosis may be oligoarticular or polyarticular and can appear
similar to RA in some patients. It most frequently affects the ankles, knees, hands, wrist, and MCP and PIP
joints, and it is frequently associated with parenchymal pulmonary disease.
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Fibroblastic rheumatism — Fibroblastic rheumatism, a rare disease of unknown etiology, shares the
features of arthralgia, arthritis, and nodules with RA [39-41]. Flexion contractures of the fingers occur in most
patients, while thickened palmar fascia is noted in about one-half of reported cases. Biopsy of a nodule or
thickened skin typically reveals increased thickness of collagen fibers and fibroblastic proliferation.
Decreased elastic fibers and the presence of myofibroblasts are noted in approximately 50 percent.
Radiographic findings are variable, but periarticular osteopenia and erosions may be noted.
Due to the rarity of fibroblastic rheumatism, there is no well-established treatment. Progressive disease may
lead to sclerodactyly and ankylosis of affected joints.
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics”
and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5th to 6th
grade reading level, and they answer the four or five key questions a patient might have about a given
condition. These articles are best for patients who want a general overview and who prefer short, easy-to-
read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more
detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want
in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail
these topics to your patients. (You can also locate patient education articles on a variety of subjects by
searching on “patient info” and the keyword(s) of interest.)
● Beyond the Basics topics (see "Patient education: Rheumatoid arthritis symptoms and diagnosis
(Beyond the Basics)" and "Patient education: Rheumatoid arthritis treatment (Beyond the Basics)" and
"Patient education: Complementary and alternative therapies for rheumatoid arthritis (Beyond the
Basics)")
● Rheumatoid arthritis (RA) should be suspected in the adult patient who presents with inflammatory
polyarthritis. The initial evaluation of such patients requires a careful history and physical examination,
along with selected laboratory testing to identify features that are characteristic of RA or that suggest an
alternative diagnosis. (See 'Evaluation for suspected RA' above and 'Differential diagnosis' above.)
● The following components of the medical evaluation are helpful in making a clinical diagnosis of RA, both
for the identification of characteristic findings and for the exclusion of other diagnoses (see 'Evaluation
for suspected RA' above):
• A thorough medical history, with particular attention to joint pain, stiffness, and associated functional
difficulties
• A complete physical examination to assess for synovitis, limited joint motion, extraarticular disease
manifestations, and signs of diseases included in differential diagnosis
• Basic and selected laboratory testing, including assays for acute phase reactants (erythrocyte
sedimentation rate [ESR] and C-reactive protein [CRP]), rheumatoid factor (RF), anti-cyclic
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• Selected imaging studies, including bilateral radiographs of the hands, wrists, and feet
● The diagnosis of RA can be made in a patient with inflammatory arthritis involving three or more joints,
positive RF and/or anti-citrullinated peptide/protein antibody, disease duration of more than six weeks,
and elevated CRP or ESR, but without evidence of diseases with similar clinical features. (See 'Our
diagnostic criteria' above.)
● RA may also be diagnosed in patients without all of the classic findings of disease. This includes patients
with seronegative RA, those with clinically quiescent disease, and those with recent onset RA. Such
patients have findings/clinical features that are generally consistent with those described as meeting the
American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR)
classification criteria for RA. (See 'Patients not meeting above criteria' above.)
● The 2010 classification criteria for RA were developed primarily for the identification for research
purposes of patients with RA who are at high risk of persistent symptoms and joint injury unless treated
with disease-modifying antirheumatic drugs (DMARDs). These criteria have replaced the 1987 criteria,
which were based only upon patients with established disease. (See 'Classification criteria' above.)
● The differential diagnosis of RA includes multiple disorders that can generally be distinguished clinically
or by limited laboratory testing, based upon a combination of the following features (see 'Differential
diagnosis' above):
REFERENCES
1. Whiting PF, Smidt N, Sterne JA, et al. Systematic review: accuracy of anti-citrullinated Peptide
antibodies for diagnosing rheumatoid arthritis. Ann Intern Med 2010; 152:456.
2. Nishimura K, Sugiyama D, Kogata Y, et al. Meta-analysis: diagnostic accuracy of anti-cyclic citrullinated
peptide antibody and rheumatoid factor for rheumatoid arthritis. Ann Intern Med 2007; 146:797.
3. Finckh A, Liang MH. Anti-cyclic citrullinated peptide antibodies in the diagnosis of rheumatoid arthritis:
bayes clears the haze. Ann Intern Med 2007; 146:816.
4. Lee DM, Schur PH. Clinical utility of the anti-CCP assay in patients with rheumatic diseases. Ann
Rheum Dis 2003; 62:870.
5. Luime JJ, Colin EM, Hazes JM, Lubberts E. Does anti-mutated citrullinated vimentin have additional
value as a serological marker in the diagnostic and prognostic investigation of patients with rheumatoid
arthritis? A systematic review. Ann Rheum Dis 2010; 69:337.
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29. Moll JM, Wright V. Psoriatic arthritis. Semin Arthritis Rheum 1973; 3:55.
30. Pease CT, Haugeberg G, Montague B, et al. Polymyalgia rheumatica can be distinguished from late
onset rheumatoid arthritis at baseline: results of a 5-yr prospective study. Rheumatology (Oxford) 2009;
48:123.
31. Mekinian A, Braun T, Decaux O, et al. Inflammatory arthritis in patients with myelodysplastic syndromes:
a multicenter retrospective study and literature review of 68 cases. Medicine (Baltimore) 2014; 93:1.
32. Chandran G, Ahern MJ, Seshadri P, Coghlan D. Rheumatic manifestations of the myelodysplastic
syndromes: a comparative study. Aust N Z J Med 1996; 26:683.
33. Barrow MV, Holubar K. Multicentric reticulohistiocytosis. A review of 33 patients. Medicine (Baltimore)
1969; 48:287.
34. Gorman JD, Danning C, Schumacher HR, et al. Multicentric reticulohistiocytosis: case report with
immunohistochemical analysis and literature review. Arthritis Rheum 2000; 43:930.
35. Matejicka C, Morgan GJ, Schlegelmilch JG. Multicentric reticulohistiocytosis treated successfully with
an anti-tumor necrosis factor agent: comment on the article by Gorman et al. Arthritis Rheum 2003;
48:864.
36. Calamia KT, Walsh JS, Bradley T, et al. Treatment of multicentric reticulohistiocytosis with etanercept: a
case report (abstract). Arthritis Rheum 2003; 48:S618.
37. Goto H, Inaba M, Kobayashi K, et al. Successful treatment of multicentric reticulohistiocytosis with
alendronate: evidence for a direct effect of bisphosphonate on histiocytes. Arthritis Rheum 2003;
48:3538.
38. Codriansky KA, Rünger TM, Bhawan J, et al. Multicentric reticulohistiocytosis: a systemic osteoclastic
disease? Arthritis Rheum 2008; 59:444.
39. Fam AG, Hanna W, Mak V, Assaad D. Fibroblastic rheumatism: clinical and histologic evolution of
cutaneous manifestations. J Rheumatol 1998; 25:2261.
40. Lee JM, Sundel RP, Liang MG. Fibroblastic rheumatism: case report and review of the literature. Pediatr
Dermatol 2002; 19:532.
41. Pedersen JK, Poulsen T, Hørslev-Petersen K. Fibroblastic rheumatism: a Scandinavian case report.
Ann Rheum Dis 2005; 64:156.
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GRAPHICS
Criterion Description
Morning Morning stiffness in and around the joints, lasting at least one hour before maximal improvement.
stiffness
Arthritis At least three joint areas (out of 14 possible areas; right or left PIP, MCP, wrist, elbow, knee, ankle,
of three or MTP joints) simultaneously have had soft tissue swelling or fluid (not bony overgrowth alone) as
more joint observed by a physician.
areas
Arthritis of At least one area swollen (as defined above) in a wrist, MCP, or PIP joint.
hand joints
Symmetric Simultaneous involvement of the same joint areas (as defined above) on both sides of the body
arthritis (bilateral involvement of PIPs, MCPs, or MTPs, without absolute symmetry is acceptable).
Rheumatoid Subcutaneous nodules over bony prominences or extensor surfaces, or in juxta-articular regions as
nodules observed by a physician.
Serum Demonstration of abnormal amounts of serum rheumatoid factor by any method for which the result
rheumatoid has been positive in less than 5 percent of normal control subjects.
factor
Radiographic Radiographic changes typical of rheumatoid arthritis on posteroanterior hand or wrist radiographs,
changes which must include erosions or unequivocal bony decalcification localised in, or most marked
adjacent to, the involved joints (osteoarthritis changes alone do not qualify).
Note: For classification purposes, a patient has RA if at least four of these criteria are satisfied (the first four must
have been present for at least six weeks).
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Lab
Diagnosis Sex Age Comments
tests
Psoriatic M=F 30-55 <20 10 percent of those with psoriatic arthritis will have an
arthritis percent RA-like distribution (MCPs, PIPs, wrists). Cutaneous
RF+ psoriasis will be evident in the vast majority of cases.
Tophaceous M>F 25-70 M 95 percent Intermittent inflammatory arthritis during the onset,
gout RF– with evolution of tophi and chronic inflammatory
polyarthritis. Elevated serum urate and tophi help
F >45 >95
distiguish from RA.
percent ↑
serum
urate
Erosive F>M >60 RF– (or Chronic polyarthritis with intermittent or sustained
inflammatory normal for inflammation affecting PIP and DIP joints. Radiographs
OA age) demonstrate distinctive erosions and evidence of OA.
Reactive M>F 16-50 95 percent See criteria for spondyloarthropathies; often associated
arthritis RF–; 50-80 with low back pain, ocular, genitourinary, or GI
(formerly known percent symptomatology and enthesitis (heel pain).
as Reiter's HLA-B27+
syndrome)
Enteropathic M=F All ages 95 percent 20 percent of patients with Crohn's disease or ulcerative
arthritis RF– colitis will develop peripheral arthritis. Diagnosis may be
difficult until GI involvment becomes apparent.
Associated with oral ulcerations, GI symptoms or other
features of spondyloarthropathy.
Polymyositis/ F>M 30-60 95 percent Chronic inflammatory arthritis uncommonly occurs early
dermatomyositis RF–; 50 in course of PM/DM. Features of proximal muscle
percent weakness, bulbar dysphagia, muscle enzyme elevation,
ANA+; 70 or skin involvement (ie, Gottron's papules) should be
percent ↑ sought.
CK
Sarcoid arthritis F>M 20-40 25 percent 15 percent of patients with sarcoidosis will develop
RF+ arthritis. Early in the disease a chronic inflammatory
oligo or polyarthritis lasting weeks to months may
develop and typically involve the ankles and knees.
Other features of sarcoidosis (ie, erythema nodosum,
hilar adenopathy) are usually apparent.
Parvovirus B19- F>M Any age <10 Adults manifest a flu-like picture, seldom develop the
associated percent "slapped-cheek" rash; arthralgias are more common
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arthritis RF+; >80 than arthritis. Arthritis is an acute inflammatory
percent polyarthritis with an RA-like distribution lasting two
anti-B19 weeks. Less than 10 percent develop a chronic
IgM inflammatory arthritis.
antibodies
(acutely)
Polymyalgia F>M >50 90 percent Proximal girdle pain and stiffness without synovitis.
rheumatica RF–; >95
percent ↑↑
ESR
ANA: antinuclear antibody; DIP: distal interphalangeal; DM: dermatomyositis; ESR: erythrocyte sedimentation rate; GI:
gastrointestinal; MCP: metacarpophalangeal; OA: osteoarthritis; PIP: proximal interphalangeal; PM: polymyositis; RA:
rheumatoid arthritis; SLE: systemic lupus erythematosus.
* 1. RA often begins insidiously with vague constitutional and musculoskeletal symptoms that may last for weeks or
months before synovitis becomes apparent.
2. During the first six months of RA, <50 percent of patients will be RF-positive, and the sensitivity of the 1987 ACR
criteria is reduced.
3. A variety of less common chronic inflammatory seronegative articular conditions may clinically resemble early RA. It
may be necessary to observe and evaluate the patient repeatedly for evolution of the disorder and manifestation of
features that will distinguish them from RA. The above disorders can mimic RA.
Data from: Lipsky P. Algorithms for the diagnosis and management of musculoskeletal complaints: A new tool for the
primary-care provider. (See www.swmed.edu/home_pages/cme/endurmat/lipsky/index.html.)
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Sausage toe (with diffuse swelling) of the second digit and mild keratoderma
blenorrhagica on the dorsum of the foot in a man with reactive arthritis
(formerly Reiter's syndrome).
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Stiffness Worse after resting (eg, morning If present, worse after effort, may be described as
stiffness) evening stiffness
CCP: cyclic citrullinated peptide; ESR: erythrocyte sedimentation rate; CRP: C-reactive protein.
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Contributor Disclosures
PJW Venables, MA, MB BChir, MD, FRCP Nothing to disclose Ravinder N Maini, BA, MB BChir, FRCP,
FMedSci, FRS Speaker's Bureau: Genentech [History of anti-TNF therapy]. Patent Holder: Inventors share
of royalties awarded by The Kennedy Trust for Rheumatology Research, UK, on anti-TNF therapy patents, by
AbbVie, Centocor/Janssen, Hospira, and Celltrion. James R O'Dell, MD Consultant/Advisory Boards:
AbbVie [Rheumatoid arthritis (TNF inhibitor)]; Lilly [Rheumatoid arthritis (JAK kinase inhibitor)]; BMS
[Rheumatoid arthritis (abatacept)]; GlaxoSmithKline [Rheumatoid arthritis (Anti-IL-6)]; Medac [Rheumatoid
arthritis (methotrexate)]. Paul L Romain, MD Nothing to disclose
Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are
addressed by vetting through a multi-level review process, and through requirements for references to be
provided to support the content. Appropriately referenced content is required of all authors and must conform
to UpToDate standards of evidence.
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