Snapshot A 20-year-old overweight woman presents to her physician’s office for a rash. She reports to wearing tight jeans despite the hot, humid weather. Physical exam reveals several annular plaques with overlying scale and central clearing on her inner thighs. A skin scraping with KOH preparation reveals hyphae. Introduction Clinical definition superficial fungal infection of the skin of the groin or inner thighs also known as jock itch Associated conditions tinea pedis often the source of infection onychomycosis Epidemiology Incidence 10-20% lifetime incidence Demographics adolescent and adult males adult females who are overweight or wear tight jeans Risk factors close contact sports, such as wrestling moist warm environment immunocompromise contact with infected animals Etiology Pathogenesis fungus infects superficial keratinized tissue and invades stratum corneum and terminal hair Dermatophytes Trichophyton most commonly Trichophyton rubrum Microsporum Epidermophyton Presentation Symptoms primary symptoms itch Physical exam can have single or multiple lesions well-demarcated annular patches or plaques with central clearing with scaling diffuse erythema location inner thighs or groin spares scrotum and mucosa Studies KOH preparation skin scrapings at active edge of lesion mixed with KOH presence of hyphae indicates fungal infection Wood lamp indications to rule out erythrasma coral-red fluorescence Diagnostic criteria diagnosis usually based on clinical history and physical exam Differential Erythrasma coral-red fluorescence under Wood lamp Cutaneous candidiasis Treatment Medical topical therapy indication localized lesions drugs terbinafine 1% approved for patients 12 years of age and older clotrimazole 1% approved for patients 2 years of age and older ketoconazole 2% oral therapy indications widespread disease refractory disease drugs terbinafine griseofulvin Complications Secondary bacterial infection Prognosis Responsive to topical treatment