Snapshot A 17-year-old boy presents to his pediatrician for evaluation of a rash in his genital area. He reports that it is very itchy and started about 1 week ago. At school, he participates in multiple sports, including wrestling with practice 3 times a week. He admits that he doesn’t always wash his hands and often delays showering after practice. On physical exam, there are multiple 3-5 cm annular and pink plaques on inner thighs and groin. His scrotum is clear. He is given a topical treatment for his rash. Introduction Clinical definition superficial fungal infection of the skin of the groin or inner thighs a type of dermatophytosis also known as jock itch 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 dermatophytes Trichophyton most commonly Trichophyton rubrum Microsporum Epidermophyton Pathogenesis fungus infects superficial keratinized tissue and invades stratum corneum and terminal hair Associated conditions tinea pedis often the source of infection onychomycosis Prognosis responsive to topical treatment 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