Snapshot A 7-year-old previously healthy boy is brought to the pediatrician with a pruritic scalp and patchy hair loss. His mother reports a close friend at school recently had similar symptoms. Physical exam shows scaly patches with alopecia and black dots. Potassium hydroxide (KOH) preparation shows fungal hyphae around hair follicles. Introduction Clinical definition superficial fungal skin infection of the scalp Epidemiology demographics most common in pre-pubertal boys more common in African Americans location on the scalp ("capitis" = "head") Etiology infectious agents are fungi called dermatophytes, including Trichophyton Microsporum acquired through direct contact with the fungus e.g., shared combs and hats Pathogenesis dermatophytes live only in keritinized tissues (hair, skin, and nails) symptoms result from host's innate immune response Prognosis excellent since most cases resolve with treatment Presentation Symptoms itchiness hair loss Physical exam single or multiple scaly patches on the scalp alopecia with small black dots from broken-off hairs cervical lymphadenopathy less common kerion inflammatory plaque with drainage and crusting favus perifollicular erythema progresses to yellow cupping Studies Labs potassium hydroxide (KOH) prep used on hairs plucked from affected areas outer hair shaft - Microsporum inner hair shaft - Trychophyton Wood lamp ultraviolet A (UVA) light if hair fluoresces Microsporum spp. is the cause if hair does not fluoresce probable cause is Trichophyton spp. Culture rarely needed can give definitive diagnosis Diagnostic criteria diagnosis typically made by physical exam Differential Alopecia areata autoimmune form of hair loss presents with patchy alopecia with black dots and without scaling Seborrheic dermatitis presents with diffuse scaling on the scalp with erythema and pruritis Psoriasis presents with scaly and erythematous plaques that are well-demarcated Treatment Conservative management of close contacts indication when multiple children are in the home treatments use of antifungal shampoo by all house members avoid sharing and clean hair clippers, combs, and hats Medical oral antifungals indication when diagnosis is made by physical exam and before culture results are available medications griseofulvin mechanism of action inhibits fungal mitosis and binds to keratin terbinafine mechanism of action inhibits fungal cell membrane ergosterol synthesis Complications May progress to kerion or favus