Tinea in Emergency Medicine in Emergency Medicine 

The dermatophytes are a group of fungi (ringworm) that invade the dead keratin of skin, hair, and nails. Several species of dermatophytes infect humans; these can be divided into superficial and deep forms. This article focuses on superficial fungal infections that mainly belong to the Epidermophyton, Microsporum, and Trichophyton genera. These are more common and more likely to be seen in the ED. More detailed information can be found in the Dermatology section on deep fungal infections that can be life threatening in presentation, most often present in those with little or no immune response ability, and require immediate dermatologic consultation.

Dermatophytosis is a superficial fungal infection caused by dermatophytes. The infection may spread from person to person (anthropophilic), animal to person (zoophilic), or soil to person (geophilic). The most common of these organisms are Trichophyton rubrum, Trichophyton tonsurans, Trichophyton interdigitale and/or Trichophyton mentagrophytes, Microsporum canis, and Epidermophyton floccosum.

The term phyton is derived from the Latin/Greek word for plant. Thus, dermato (skin) phyte (plant) was generated as a descriptive early term for tinea on the skin.

The term tinea is derived from the Latin word for worm or larvae.

Dermatophytes are keratinophilic fungi and have the ability to invade keratinized tissue (eg, hair, nails, any area of the skin) but are restricted to the dead cornified layer of the epidermis. Humid or moist skin provides a very favorable environment for the establishment of fungal infection. Clinically, tinea infections are classified according to the body region involved/infected:

• Tinea capitis - Scalp (shown in the image below)Gray-patch ringworm (microsporosis) is an ectothrix infection or prepubertal tinea capitis seen here in an African American male child. Gray patch refers to the scaling with lack of inflammation, as noted in this patient. Hairs in the involved areas assume a characteristic dull, grayish, discolored appearance. Infected hairs are broken and shorter. Papular lesions around hair shafts spread and form typical patches of ring forms, as shown. Culture from the lesional hair grew Microsporum canis.
• Tinea corporis - Trunk and extremities (shown in the image below)Annular plaque (tinea corporis).
• Tinea manuum and tinea pedis - Palms, soles, and interdigital webs
• Tinea cruris - Groin
• Tinea barbae - Beard area and neck
• Tinea faciale - Face
• Tinea unguium (onychomycosis) - Nail

Descriptive clinical diagnoses also exist and are based on old derivations of terminology. One example is tinea imbricata, which forms geometric patterns on the skin.^[1]

The specific etiologic agent is often associated with a specific region of infection. Further elaboration of the discussion below can be found in the tinea articles of the eMedicine Dermatology volume (Tinea Barbae, Tinea Capitis, Tinea Corporis, Tinea Cruris, Tinea Faciei, Tinea Nigra, Tinea Pedis, Tinea Versicolor).

Tinea capitis caused by the species of genera Trichophyton and Microsporum) is the most common pediatric dermatophyte infection. The age predilection is believed to result from the lack of certain flora and fungistatic sebum in this age (Pityrosporum orbiculare [Pityrosporum ovale]) and short/medium chain fatty acids.)

From the site of inoculation, the fungal hyphae grow centrifugally in the stratum corneum and down into the hair as they invade newly forming keratin. It usually takes 2 weeks to produce clinically visible changes.

The natural course of tinea capitis is of a spontaneous cure at puberty, once sebum production begins.

Hair invasion is divided into 3 types. The site of formation of the arthroconidia (spore-forming bodies) classifies the species causing the invasion. They are as follows:

• Ectothrix species: Conidia form on the exterior of the hair shaft. The cuticle is destroyed and involved areas fluoresce a green-yellow under a Wood lamp. This is caused by Microsporum canis, Microsporum distortum, Microsporum ferrugineum, Microsporum audouinii, as well as nonfluorescent Trichophyton rubrum,Trichophyton verrucosum, Trichophyton megninii, Trichophyton mentagrophytes, Microsporum gypseum, and Microsporum nanum.
• Endothrix species: Conidia form within the hair shaft, and each is filled with hyphae and spores. The cuticle is not affected, and hairs do not fluoresce under a Wood lamp. This is caused by anthropophilic (Trichophyton rubrum, Trichophyton gourvilii, Trichophyton tonsurans,Trichophytonviolaceum,Trichophyton yaoundei, Trichophyton soudanense).
• Favus species: Hyphae arrange within and around the hair shaft. This is a rare and severe form resulting in favus-like crusts or scutula and hair loss with honey comb destruction pattern of the follicles. This is caused by Trichophyton schoenleinii.
• Kerion: Thick plaques and boggy skin that form often with bacterial infection superimposed. Mainly caused by Microsporum canis.^[2] This pattern develops in such a manner that it is often believed to be a response to the dermatophyte.
• Lupoid sycosis: Chronic recalcitrant impetigo/folliculitis can result in sycosis barbae (similar to lupoid sycosis), with scarring and presentation similar to discoid lupus. Tinea may also cause this presentation.

Frequency

United States

Fungal infection occurs worldwide. Tinea pedis is the most common type in the United States and in the rest of the world.

Tinea capitis (ringworm of the head) is the most common dermatophytosis of childhood.

Tinea corporis is present in all ages, although it is more frequent in adolescents and pregnant females.

Onychomycosis is a common problem, especially in adults. In a survey in the United States, the prevalence of onychomycosis was approximately 3% in males and 1.4% in females. In a sample of North American children, 0.44% had onychomycosis.^[3]

International

International prevalence of tinea has ranged from 1-14%.^{[4, 5]}

T rubrum is the most common cause of tinea corporis, tinea cruris, tinea pedis, and nail infection worldwide.

Mortality/Morbidity

• Cellulitis in the lower extremities, which causes a breach in the skin and allows the inoculation of opportunistic bacteria, is a frequent complication of interdigital fungal infection.
• In patients with impaired cell-mediated immune function, atypical and locally aggressive presentations of dermatophyte infection may occur. These include extensive skin disease, subcutaneous abscesses, and dissemination.

Race

Fungal infection affects all races; however, the prevalence of organisms varies by country.

Sex

Both sexes are affected by fungal infection. Tinea cruris is much more common in males because of the male anatomy, which allows moisture to accumulate in the crural folds.

Age

• Fungal infection affects all ages.
• Tinea capitis mainly is a disease in children; however, adults can be affected.
• Tinea cruris, tinea pedis, and onychomycosis predominantly affect the adult population.