Snapshot An 11-year-old previously healthy girl presents with a circular lesion on her body. She does not report any itchiness or pain. Her mother reports that the patient's 8-year-old brother has had an itchy scalp and patchy hair loss over the last two weeks. On physical exam, the lesion appears with concentric rings, with scale on the periphery. The physician collects scrapings of the lesion and performs a potassium hydroxide preparation. Under microscopy, multiple septated hyphae are observed. Introduction Clinical definition superficial fungal infection of the skin "corporis" = "body" affected areas include the trunk, legs, arms, and neck does not include the feet, hands, groin, nails, and scalp these tinea infections are classified differently Epidemiology demographics most common in pre-adolescents classically in athletes with skin-to-skin contact (wrestlers) risk factors exposure to an infected person or animal may be acquired from tinea capitis this is the most common cause in children immunocompromised state Etiology dermatophyte fungal infection most commonly from the trychophyton and microsporum genera trychophyton rubrum is the most common caused by direct contact with the fungus infection on another person or animal especially kittens and puppies infection from another location e.g. tinea cruris, tinea pedis, etc. Pathogenesis infection of the epidermis occasionally spreads to the hair follicles Prognosis excellent most cases resolve with treatment Presentation Symptoms single or multiple pruritic areas of rash may be asymptomatic Physical exam begins as an erythematous, scaly patch or plaque in a circular or oval shape spreads outward, with central clearing sharply marginated with a raised border that advances multiple lesions may coalesce may become extensive should raise suspicion for immune compromise may be inflammatory with significant erythema more common in infection from animals Studies Labs potassium hydroxide (KOH) prep commonly done to confirm diagnosis performed on scrapings from lesions will show characteristic segmented hyphae of dermatophytes Culture may be used for definitive diagnosis Differential Diagnosis Subacute cutaneous lupus erythematosus will be erythematous, ring-shaped, scaly plaques on sun-exposed skin Granuloma annulare benign inflammatory condition will have multiple erythematous plaques on the extremities does not exhibit scaling Pitariasis rosea will show circular, erythematous lesions and may exhibit scaling scale will appear as "collarette" may show "christmas tree-like" distribution on back, following lines of tension Treatment Medical topical antifungal medications azoles terbinafine naftifine note, topical nystatin is not effective against dermatophytes mechanism of action azoles inhibit fungal cell membrane formation disrupts biosynthesis of ergosterol terbinafine blocks fungal cell wall production inhibits squalene epoxidase systemic antifungal therapy indication extensive skin involvement failure of topical therapy medications itraconazole terbinafine Prognosis, Prevention and Complications Infection may be extensive in the setting of underlying immunodeficiency e.g. HIV/AIDS, diabetes