Dermatophytosis overview

# Overview
Dermatophytosis is a fungal infection of the skin. It gets worse during summer and the symptoms are  alleviated during winter. Dermatophytes of the genera Trichophyton and Microsporum are the most common causative agents. Mode of transmission of Dermatophytes  is via direct or indirect contact with skin (or) scalp lesions of infected people,animals (or) fomites. Following transmission, the dermatophytes use proteases to adhere to the stratum corneum of the skin. Penetration by dermatophytes is achieved by secreting multiple serine-subtilisins and metallo-endoproteases (fungalysins) formerly called keratinases that are found only in the dermatophytes. Acutely, the host responds to fungal invasion by Type IV delayed type hypersensitivity reaction (also known as "Trichophytin reaction") leading to a cell mediated response. Dermatophytosis should be differentiated from other superficial skin infections which may all present as a red, pruritic, annular and scaly rash on different parts of the body such as tinea versicolor, tinea nigra, white piedra, black piedra, superficial candidiasis. Tinea corporis should also be differentiated from other annular skin eruptions, especially subacute cutaneous lupus erythematosus (SCLE), granuloma annulare, and erythema annulare centrifugum. Worldwide, the prevalence of dermatophytosis is 20000-25000 per 100,000 persons. The common risk factors for dermatophytosis are xerosis (dry skin), skin-skin contact with an infected person, contact with infected pets, topical immunosupressive drugs, low socioeconomic status, occlusive footwear, high humidity, rural settlement, poor hygiene, excessive sweating, public showers, obesity, diabetes mellitus. The skin is characterized by erythematous, papulosquamous, annular, well-ircumscribed, superficial rash with central clearing which may be located on the scalp, neck, trunk, extremities and groin. Laboratory findings consistent with the diagnosis of dermatophytosis include KOH preparation showing refractile, long, smooth, undulating, branching, and septate hyphal filaments with or without arthroconidiospores; culture and sensitivity may yield the diagnosis but it takes 7-14 days for colony growth; hemotoxylin and eosin stain may be used in diagnosis of Majocchi's granuloma in which KOH examination of scales may be false negative. Polymerase chain reaction (PCR) testing may be used to identify various dermatophytic infections and even help in evaluating drug resistances of different species of dermatophytes. The mainstay of therapy for dermatophytosis is topical antifungals. Topical Antifungalrug|antifungals]] include imidazoles, allylnines and other agents including ciclopirox olamine, benzoic acid preparations (Whitfield's ointment), tolnaftate, haloprogin, drying agents and salicylic acid. In some situations, systemic antifungal therapy may be used for dermatophytosis which includes griseofulvin, ketoconazole, terbinafine, itraconazole and fluconazole. Effective measures for the primary prevention of dermatophytosis include avoiding sharing clothing, sports equipment, towels or sheets of infected individuals. Washing clothes worn by infected individuals with fungicidal soap and avoiding infected pets.

# Historical Perspective
Dermatophytosis was first described by David Gruby, a Hungarian physician, in 1841. Before Gruby, various scientists described lesions which were ring-like, and were thought to be infective. The description of lesions dates back to the Roman era. Around 1890, Raimond Sabouraud advanced knowledge of dermatomycology by studying extensively into the taxonomy, morphology, and treatment of dermatophytes, even classifying these fungal agents into four genera (three of which are still current to mycologists). Dermatophytosis has been prevalent as early as the year 1906 and before. At that 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 antiparasitic medication.

# Classification
A number of different species of fungi are involved. Dermatophytes of the genera Trichophyton and Microsporum are the most common causative agents.

# Pathophysiology
Dermatophytes are usually transmitted via contact to human host. Following transmission, the dermatophytes use proteases to adhere to the stratum corneum of the skin. Penetration by dermatophytes is achieved by secreting multiple serine-subtilisins and metallo-endoproteases (fungalysins) formerly called keratinases that are found only in the dermatophytes. Acutely, the host responds to fungal invasion by Type IV delayed type hypersensitivity reaction (also known as "Trichophytin reaction") leading to a cell mediated response. Fungus secreted proteases are one of the most important virulence factors of dermatophytes and are thought to be responsible for evasion from host defense mechanisms. Secreted subtilisin proteases expressed in the dermatophytes could play a role in keratin degradation. Dermatophyte infections of the skin surface         (tinea corporis and tinea faciei) mostly present as erythematous, scaly papules that gradually progress to annular or circular red patches or plaques, with central clearing and scaling at the periphery. On microscopic examination of the skin, there may be neutrophils retained in the stratum corneum, parakeratosis, spongiosis and dermal edema.

# Causes
Dermatophytes cause non-lethal infection of the superficial skin, therefore, the agents causing dermatophytosis are not life-threatening. Common genera of dermatophytes causing infections include the Epidermophyton, Microsporum and Trichophyton. Causes of dermatophytosis according to the organ system involvement include, tinea corporis which is infection of body surfaces other than the feet, groin, face, scalp hair, or beard hair; Tinea pedis which is infection of the foot; tinea cruris which is infection of the groin; tinea capitis which is infection of scalp hair; tinea unguium (dermatophyte onychomycosis) which signifies infection of the nail; tinea faecei which is infection of the face; tinea barbae which is infection of the facial hair; tinea mannum which includes infection of the hands.

# Differential Diagnosis
Dermatophytosis should be differentiated from other superficial skin infections which may all present as a red, pruritic, annular and scaly rash on different parts of the body such as tinea versicolor, tinea nigra, white piedra, black piedra, superficial candidiasis. Tinea corporis should also be differentiated from other annular skin eruptions, especially subacute cutaneous lupus erythematosus (SCLE), granuloma annulare, and erythema annulare centrifugum.

# Epidemiology and Demographics
Worldwide, the prevalence of dermatophytposis is 20000-25000 per 100,000 persons. Dermatophytosis commonly affects school-aged (5-15 years of age) children. Overall, dermatophytosis is more prevalent in women than in men. Scalp infections are more common in blacks as compared to Caucasians. There is a large variation in the type on dermatophytosis affecting individuals, depending upon the geographic location.

# Risk Factors
The common risk factors for dermatophytosis are xerosis (dry skin), skin-skin contact with an infected person, contact with infected pets, topical immunosupressive drugs, low socioeconomic status, occlusive footwear, high humidity, rural settlement, poor hygiene, excessive sweating, public showers, obesity, diabetes mellitus. Less common risk factors for dermatophytosis are occupational (farmer, worker and retired), presence of fungal infection in family, cancer and psoriasis.

# Screening
According to the the U.S. Preventive Service Task Force (USPSTF), there is insufficient evidence to recommend routine screening for dermatophytosis but the wood lamp examination may be used as a screening tool for tinea capitis in suspected cases.

# Natural History, Complications and Prognosis
Dermatophytosis tends to get worse during summer, with the symptoms alleviating during winter. Skin medicine usually treats ringworm within 4 weeks. If the ringworm infection is severe or it does not respond well to self-care, it will usually respond quickly to antifungal pills.

# Diagnosis

## History and Symptoms
The hallmark of dermatophytosis is an enlarged, raised red ring with central clearing. Infection on the skin of the feet may cause athlete's foot and infection of the groin area may result in jock itch. Involvement of the nails is termed onychomycosis, and they may thicken, discolor, and finally crumble or fall off.

## Physical Examination
Patients are usually well-appearing in dermatophytosis. The skin is characterized by erythematous, papulosquamous, annular, well-circumscribed, superficial rash with central clearing which may be located on the scalp, neck, trunk, extremities and groin. Abnormalities of the head/hair may include, dry scaling, which may be similar to seborrheic dermatitis; black dots, which are areas of broken hair on a scaly surface; smooth areas of hair loss. Neck in tinea corporis may show, red, itchy, scaly, circular skin rash and cervical lymphadenopathy. Genitals may be involved in tinea cruris and examination may show pustules and vesicles at the active edge of the infected area along with maceration. Hands in tinea mannum may show dry and hyperkeratotic palmar surface. Feet in tinea pedis may show fissuring, maceration, and scaling in the interdigital spaces of the fourth and fifth toes.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of dermatophytosis include KOH preparation showing refractile, long, smooth, undulating, branching, and septate hyphalfilaments with or without arthroconidiospores; culture and sensitivity may yield the diagnosis but it takes 7-14 days for colony growth; hemotoxylin and eosin stain may be used in diagnosis of Majocchi's granuloma in which KOH examination of scale may be false negative. Polymerase chain reaction (PCR) testing may be used to identify various dermatophytic infections and even help in evaluating drug resistances of different species of dermatophytes.

## X-ray
There are no X-ray findings associated with dermatophytosis.

## CT-scan
There are no CT scan findings associated with dermatophytosis.

## MRI
There are no MRI findings associated with dermatophytosis.

## Other Imaging studies
There are no other imaging studies associated with dermatophytosis.

## Other Diagnostic Studies
Most of the time, ringworm can be diagnosed by looking at the skin. Other diagnostic studies that can be used to diagnose dermatophytosis are matrix-assisted laser desorption ionization test and reflectance confocal microscopy.

# Treatment

## Medical therapy
The mainstay of therapy for dermatophytosis is topical antifungals. Topical antifungals include imidazoles, allylnines and other agents including ciclopirox olamine, benzoic acid preparations (Whitfield's ointment), tolnaftate, haloprogin, drying agents and salicylic acid. In some situations, systemic antifungal therapy may be used for dermatophytosis which includes griseofulvin, ketoconazole, terbinafine, itraconazole and fluconazole.

## Surgery
Surgery is not the first-line treatment option for patients with dermatophytosis. Surgical drainage of superficial vesicles, bullae, and pustules may be done.

## Primary prevention
Effective measures for the primary prevention of dermatophytosis include avoiding sharing clothing, sports equipment, towels or sheets of infected individuals. Washing clothes worn by infected individuals with fungicidal soap and avoiding infected pets.

## Secondary prevention
Secondary prevention of dermatophytosis is similar to primary prevention.