Dermatophytosis

Dermatophytosis, also known as tinea and ringworm, is a fungal infection of the skin^[2] (a dermatomycosis), that may affect skin, hair, and nails.^[1] Typically it results in a red, itchy, scaly, circular rash.^[1] Hair loss may occur in the area affected.^[1] Symptoms begin four to fourteen days after exposure.^[1] The types of dermatophytosis are typically named for area of the body that they affect.^[2] Multiple areas can be affected at a given time.^[4]

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Quick Facts Other names, Specialty ...

Dermatophytosis
Other names	Ringworm, tinea
Ringworm on a human leg
Specialty	Dermatology, Internal Medicine
Symptoms	Red, itchy, scaly, circular skin rash[1]
Causes	Fungal infection[2]
Risk factors	Using public showers, contact sports, excessive sweating, contact with animals, obesity, poor immune function[3][4]
Diagnostic method	Based on symptoms, microbial culture, microscopic examination[5]
Differential diagnosis	Dermatitis, psoriasis, pityriasis rosea, tinea versicolor[6]
Prevention	Keep the skin dry, not walking barefoot in public, not sharing personal items[3]
Treatment	Antifungal creams (clotrimazole, miconazole)[7]
Frequency	20% of the population[8]

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About 40 types of fungus can cause dermatophytosis.^[2] They are typically of the Trichophyton, Microsporum, or Epidermophyton type.^[2] Risk factors include using public showers, contact sports such as wrestling, excessive sweating, contact with animals, obesity, and poor immune function.^[3][4] Ringworm can spread from other animals or between people.^[3] Diagnosis is often based on the appearance and symptoms.^[5] It may be confirmed by either culturing or looking at a skin scraping under a microscope.^[5]

Prevention is by keeping the skin dry, not walking barefoot in public, and not sharing personal items.^[3] Treatment is typically with antifungal creams such as clotrimazole or miconazole.^[7] If the scalp is involved, antifungals by mouth such as fluconazole may be needed.^[7]

Dermatophytosis has spread globally, and up to 20% of the world's population may be infected by it at any given time.^[8] Infections of the groin are more common in males, while infections of the scalp and body occur equally in both sexes.^[4] Infections of the scalp are most common in children while infections of the groin are most common in the elderly.^[4] Descriptions of ringworm date back to ancient history.^[9]

A number of different species of fungus are involved in dermatophytosis. Dermatophytes of the genera Trichophyton and Microsporum are the most common causative agents. These fungi attack various parts of the body and lead to the conditions listed below. The Latin names are for the conditions (disease patterns), not the agents that cause them. The disease patterns below identify the type of fungus that causes them only in the cases listed:

• Dermatophytosis
  • Tinea pedis (athlete's foot): fungal infection of the feet
  • Tinea unguium: fungal infection of the fingernails and toenails, and the nail bed
  • Tinea corporis: fungal infection of the arms, legs, and trunk
  • Tinea cruris (jock itch): fungal infection of the groin area
  • Tinea manuum: fungal infection of the hands and palm area
  • Tinea capitis: fungal infection of the scalp and hair
  • Tinea faciei (face fungus): fungal infection of the face
  • Tinea barbae: fungal infestation of facial hair
• Other superficial mycoses (not classic ringworm, since not caused by dermatophytes)
  • Tinea versicolor: caused by Malassezia furfur
  • Tinea nigra: caused by Hortaea werneckii

Infections on the body may give rise to typical enlarging raised red rings of ringworm. Infection on the skin of the feet may cause athlete's foot and in the groin, jock itch. Involvement of the nails is termed onychomycosis.

Animals including dogs and cats can also be affected by ringworm, and the disease can be transmitted between animals and humans, making it a zoonotic disease.

Specific signs can be:

• red, scaly, itchy or raised patches
• patches may be redder on outside edges or resemble a ring
• patches that begin to ooze or develop a blister
• bald patches may develop when the scalp is affected

Fungi thrive in moist, warm areas, such as locker rooms, tanning beds, swimming pools, and skin folds; accordingly, those that cause dermatophytosis may be spread by using exercise machines that have not been disinfected after use, or by sharing towels, clothing, footwear, or hairbrushes.

Dermatophyte infections can be readily diagnosed based on the history, physical examination, and potassium hydroxide (KOH) microscopy.^[10]

Advice often given includes:

• Avoid sharing clothing, sports equipment, towels, or sheets.
• Wash clothes in hot water with fungicidal soap after suspected exposure to ringworm.
• Avoid walking barefoot; instead wear appropriate protective shoes in locker rooms and sandals at the beach.^[11][12][13]
• Avoid touching pets with bald spots, as they are often carriers of the fungus.

Antifungal treatments include topical agents such as miconazole, terbinafine, clotrimazole, ketoconazole, or tolnaftate applied twice daily until symptoms resolve — usually within one or two weeks.^[16] Topical treatments should then be continued for a further 7 days after resolution of visible symptoms to prevent recurrence.^[16][17] The total duration of treatment is therefore generally two weeks,^[18][19] but may be as long as three.^[20]

In more severe cases or scalp ringworm, systemic treatment with oral medications (such as itraconazole, terbinafine, and ketoconazole) may be given.^[21]

To prevent spreading the infection, lesions should not be touched, and good hygiene maintained with washing of hands and the body.^[22]

Misdiagnosis and treatment of ringworm with a topical steroid, a standard treatment of the superficially similar pityriasis rosea, can result in tinea incognito, a condition where ringworm fungus grows without typical features, such as a distinctive raised border.^{[citation needed]}

Dermatophytosis has been prevalent since before 1906, at which time ringworm was treated with compounds of mercury or sometimes sulfur or iodine. Hairy areas of skin were considered too difficult to treat, so the scalp was treated with X-rays and followed up with antifungal medication.^[23] Another treatment from around the same time was application of Araroba powder.^[24]

The most common term for the infection, "ringworm", is a misnomer, since the condition is caused by fungi of several different species and not by parasitic worms.

Ringworm caused by Trichophyton verrucosum is a frequent clinical condition in cattle. Young animals are more frequently affected. The lesions are located on the head, neck, tail, and perineum.^[25] The typical lesion is a round, whitish crust. Multiple lesions may coalesce in "map-like" appearance.

• 
  Multiple lesions, head
• 
  Around the eyes and on ears
• 
  On cheeks: crusted lesion (right)
• 
  Old lesions, with regrowing hair
• 
  On neck and withers
• 
  On perineum

Clinical dermatophytosis is also diagnosed in sheep, dogs, cats, and horses. Causative agents, besides Trichophyton verrucosum, are T. mentagrophytes, T. equinum, Microsporum gypseum, M. canis, and M. nanum.^[26]

Dermatophytosis may also be present in the holotype of the Cretaceous eutriconodont mammal Spinolestes, suggesting a Mesozoic origin for this disease.

Worldwide, superficial fungal infections caused by dermatophytes are estimated to infect around 20-25% of the population and it is thought that dermatophytes infect 10-15% of the population during their lifetime.^[31][32] The highest incidence of superficial mycoses result from dermatophytoses which are most prevalent in tropical regions.^[31][33] Onychomycosis, a common infection caused by dermatophytes, is found with varying prevalence rates in many countries.^[34] Tinea pedis + onychomycosis, Tinea corporis, Tinea capitis are the most common dermatophytosis found in humans across the world.^[34] Tinea capitis has a greater prevalence in children.^[31] The increasing prevalence of dermatophytes resulting in Tinea capitis has been causing epidemics throughout Europe and America.^[34] In pets, cats are the most affected by dermatophytosis.^[35] Pets are susceptible to dermatophytoses caused by Microsporum canis, Microsporum gypseum, and Trichophyton.^[35] For dermatophytosis in animals, risk factors depend on age, species, breed, underlying conditions, stress, grooming, and injuries.^[35]

Numerous studies have found Tinea capitis to be the most prevalent dermatophyte to infect children across the continent of Africa.^[32] Dermatophytosis has been found to be most prevalent in children ages 4 to 11, infecting more males than females.^[32] Low socioeconomic status was found to be a risk factor for Tinea capitis.^[32] Throughout Africa, dermatophytoses are common in hot- humid climates and with areas of overpopulation.^[32]

Chronicity is a common outcome for dermatophytosis in India.^[33] The prevalence of dermatophytosis in India is between 36.6 and 78.4% depending on the area, clinical subtype, and dermatophyte isolate.^[33] Individuals ages 21–40 years are most commonly affected.^[33]

A 2002 study looking at 445 samples of dermatophytes in patients in Goiânia, Brazil found the most prevalent type to be Trichophyton rubrum (49.4%), followed by Trichophyton mentagrophytes (30.8%), and Microsporum canis (12.6%).^[36]

A 2013 study looking at 5,175 samples of Tinea in patients in Tehran, Iran found the most prevalent type to be Tinea pedis (43.4%), followed by Tinea unguium. (21.3%), and Tinea cruris (20.7%).^[37]

• Lichen planus—An autoimmune disease that produces similar skin blotching to ringworm.
• Mycobiota—A group of all the fungi present in a particular niche like the human body.