A 59-year-old man presents with itching in the groin (Figure 139-1). On examination, he was found to have scaly erythematous plaques in the inguinal area. A skin scraping was treated with Swartz-Lamkins stain and the dermatophyte was highly visible under the microscope (Figure 139-2). He was treated with a topical antifungal medicine until his tinea cruris resolved.

Tinea cruris is an intensely pruritic superficial fungal infection of the groin and adjacent skin.

Crotch rot and jock itch.

• Using data from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey (NHAMCS) (1995-2004), there were more than 4 million annual visits for dermatophytoses and 8.4% were for tinea cruris.1
  
• Tinea cruris is more common in men than women (three-fold) and rare in children.

• Most commonly caused by the dermatophytes: Trichophyton rubrum, Epidermophyton floccosum, Trichophyton mentagrophytes, and Trichophyton verrucosum. T. rubrum is the most common organism.2
  
• Can be spread by fomites, such as contaminated towels.
  
• The fungal agents cause keratinases, which allow invasion of the cornified cell layer of the epidermis.2
  
• Autoinoculation can occur from fungus on the feet or hands.

• Wearing tight-fitting or wet clothing or underwear has traditionally been suggested; however, in a study of Italian soldiers, none of the risk factors analyzed (e.g., hyperhidrosis, swimming pool attendance) were significantly associated with any fungal infection.3
  
• Obesity and diabetes mellitus may be risk factors.4

Clinical Features

The cardinal features are scale and signs of inflammation. In light-skinned persons inflammation often appears pink or red and in dark-skinned persons the inflammation often leads to hyperpigmentation (Figures 139-3 and 139-4). Occasionally, tinea cruris may show central sparing with an annular pattern as in Figure 139-5, but most often is homogeneously distributed as in Figures 139-3 and 139-4.