Background
Tinea cruris (sometimes referred to as jock itch), a pruritic superficial fungal infection of the groin and adjacent skin, is the second most common clinical presentation for dermatophytosis. It is most commonly caused by Trichophyton rubrum or Epidermophyton floccosum; less commonly, Trichophyton mentagrophytes or Trichophyton verrucosum is involved. Trichophyton indotineae (formerly classified as T mentagrophytes genotype VIII) was first delineated in southern Asia in 2014 and is spreading worldwide. [1] Tinea cruris is a common and important clinical problem that may, at times, be a diagnostic and therapeutic challenge. Treatment is a particular concern when T indotineae is involved.
Uncomplicated tinea cruris can usually be successfully treated with topical antifungal agents. (See Treatment.) Patients who are unable to use topical treatments consistently or who have extensive or recalcitrant infection may considered candidates for systemic antifungal therapy. Prevention of reinfection is an essential component of disease management.
Other types of tinea include tinea barbae, tinea capitis, tinea corporis, tinea faciei, tinea nigra, tinea pedis, and tinea versicolor.
Pathophysiology
Tinea cruris is a contagious infection transmitted by fomites (eg, from contaminated towels or hotel bedroom sheets) or by autoinoculation from a reservoir on the hands or feet (eg, tinea manuum, tinea pedis, or tinea unguium). The etiologic agents in tinea cruris produce keratinases, which allow invasion of the cornified cell layer of the epidermis. The host immune response may prevent deeper invasion. Risk factors for initial tinea cruris infection or reinfection include wearing tight-fitting or wet clothing or undergarments. [2] Tinea cruris may be spread from person to person, especially when it is caused by T indotineae, and sexual transmission is suggested. [1]
Etiology
The dermatophyte T rubrum is the most common etiologic agent for tinea cruris, [3] though T mentagrophytes is becoming increasingly prevalent in this setting. [4] In a 2001 Brazilian series, T rubrum was the prevalent dermatophyte in 90% of the tinea cruris cases, followed by T tonsurans (6%) and T mentagrophytes (4%). [5] T indotineae can cause refractory tinea cruris. [6]
Other organisms, including E floccosum and T verrucosum, cause an identical clinical condition. T rubrum and E floccosum infections are more apt to become chronic and noninflammatory, whereas T mentagrophytes infection is often associated with an acute inflammatory clinical presentation.
Epidemiology
United States and international statistics
In a 2004 study by Foster et al, dermatophytosis accounted for approximately 10-20% of all visits to dermatologists in the United States from 1999 to 2002. [7] For the period from 2005 to 2014, dermatophyte infections were responsible for 4,981,444 outpatient visits in the United States. [4] In a 2024 study using data from a major US commercial laboratory (Labcorp), Zarzeka et al reported 2026 cases of tinea cruris for the period from March 1, 2019, to March 1, 2023 [8] ; T rubrum was the most commonly isolated pathogen (77.6%), followed by T tonsurans (14.5%).
Tinea cruris has a worldwide distribution but is found more commonly in hot humid climates. [9, 10] A study from Iran found that tinea cruris was the second most common dermatophyte infection (after tinea corporis) in Tehran for the period from 2010 to 2020. [11]
Age- and sex-related demographics
Adults are affected by tinea cruris much more commonly than children are. However, the prevalence of several risk factors for tinea cruris, such as obesity and diabetes mellitus, is rapidly increasing among adolescents. [12]
Tinea cruris is three times more common in men than in women. [8]
Prognosis
The prognosis for patients with tinea cruris is excellent with appropriate diagnosis and treatment; however, recurrence is likely if the groin region is not kept dry.
No mortality is associated with tinea cruris. Associated pruritus leads to morbidity resulting from lichenification, secondary bacterial infection, and irritant and allergic contact dermatitis caused by topically applied medications.
Patient Education
Efforts should be made to educate patients about the risks of sharing sheets and undergarments with others and about the need to keep the groin region dry (see Prevention).
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Tinea cruris.
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Tinea cruris.
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Tinea cruris.
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Tinea cruris (hematoxylin and eosin stain).
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Tinea cruris (periodic acid-Schiff stain, magnification X 20).
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Tinea cruris (Gomori methenamine-silver stain, magnification X 20).
