• Clinical science

Dermatophyte infections (Dermatophytoses)

Abstract

Dermatophyte infections, also known as tinea, are the most common fungal infections of the skin, hair, and nails. The term “dermatophyte” refers to fungal species that infect keratinized tissue, and includes members of the Trichophyton, Microsporum, and Epidermophyton genera. Tinea are classified based on their location (e.g., tinea pedis occurs on the feet and tinea capitis on the scalp). Children and immunocompromised individuals are more likely to contract tinea infections, especially tinea capitis. However, people of all ages may suffer from tinea pedis or tinea unguium. The clinical features of dermatophyte infection include pruritus, scaling, and erythema. The best initial test for the diagnosis of dermatophyte infection is potassium hydroxide (KOH) preparation, which allows segmented hyphae to be seen on microscopy. Generally, the treatment for dermatophyte infections is topical antifungals. Oral antifungals (e.g., terbinafine, griseofulvin) are always used in tinea capitis and are also used for severe, refractory cases of other kinds of tinea. Concomitant tinea infections in household members or pets should be treated as well.

Tinea versicolor, despite its name, is not caused by dermatophytes and is discussed in another learning card.

Overview

General

Diagnosis of dermatophyte infections

Treatment of dermatophyte infections

Because topical treatments are unable to penetrate the hair shaft, systemic therapy with oral antifungals such as griseofulvin or terbinafine is necessary in tinea capitis!

To prevent tinea infections from spreading, contaminated objects should not be shared (e.g., shoes, combs). Other members of the household and pets who are infected should also receive treatment!
References:[1][2][3][4][5]

Tinea

Tinea pedis (athlete's foot)

  • Definition: dermatophyte infection of the foot
  • Epidemiology
    • Affects adults and adolescents
    • Most common tinea infection
  • Predisposing factors
    • Closed, tight footwear
    • Public showers
  • Clinical features by type
  • Diagnosis and treatment: See the overview of dermatophyte infections above.
  • Complication: secondary bacterial superinfection (e.g., erysipelas)
  • Prevention
    • Foot powders and open shoes in warm, humid weather
    • Antifungal treatment of shoes
    • Footwear for public showers

Tinea corporis (ringworm)

  • Definition: dermatophyte infection affecting a location other than feet, scalp, nails, and groin
  • Predisposing factors
    • Contact with infected individuals or animals
    • Moist environments (e.g., public swimming pool facilities)
  • Clinical presentation
    • Initially round, pruritic, erythematous plaque that grows centrifugally
    • Develops into round, pruritic plaque with central clearing and a scaling, raised border
  • Diagnosis and treatment: See the overview of dermatophyte infections above.

Tinea capitis

Favus

  • Definition
    • Chronic infection caused by Trichophyton schoenleinii
    • Severe form of tinea capitis
  • Epidemiology: more common in Africa, the Middle East, and the Mediterranean
  • Clinical presentation: formation of yellow, malodorous crust with subsequent scarring alopecia
  • Treatment

Tinea unguium (onychomycosis)

The successful treatment of onychomycosis involves not only the elimination of sources of infection, but also the promotion of personal hygiene, the disinfection of footwear, and the elimination of predisposing factors!

Tinea cruris (jock itch)


References:[1][6][7][8][8][9][10][11]

Differential diagnoses

[2][3]

The differential diagnoses listed here are not exhaustive.