Dermatophyte (ring worm) fungi
Dermatophytes or ringworm fungi invade keratin and cause skin and nail infections.
Tinea Capitis: Tinea capitis is a ringworm infection of the scalp, which occurs in small children especially of African origin. Infection is spread by close contact. Lesions are single or multiple erythematous, scaly, well-demarcated patches on the scalp that gradually spread. Hairs within the patch break off giving a patch of alopecia. A kerion is a boggy swollen mass containing pus and exudate. It is a form of immune response to the fungus. Prolonged courses of oral terbinafine, itraconazole or griseofulvin are effective even in kerion.
Tinea Pedis: Tinea pedis or athlete’s foot is the most common dermatophyte infection. Infection is spread by contact with shed spores. Patients develop itchy or painful, erythematous scaling lesions between the toes. It may be acute self-limiting or a persistent chronic infection. Topical antifungal agents are usually effective if applied regularly.
Tinea Unguium: Nail infection with ringworm is common especially in the elderly. Patients develop asymmetrical discoloured (white/yellowish black) thickened nails with crumbling white material under the nail plate. This condition may respond to a prolonged course of systemic antifungals as for tinea capitis.
Tinea Cruris: Tinea cruris affects the groin with erythema and scaling is surrounded by a well-defined edge. Infection may extend over the perianal region. If mild, treatment is with topical antifungals. Severe or refractory cases require oral antifungals as for tinea capitis.