Tinea corporis is a superficial fungal skin infection of the body caused by dermatophytes. The ability of the dermatophyte to attach to the keratinized tissue of skin forms the basis for the dermatophytoses.  The dermatophytes causing tinea corporis belong to genera Trichophyton, Epidermophyton, and Microsporum. Trichophyton rubrum is the most common species to cause dermatophyte infections.

Other common isolates include Trichophyton mentagrophytes and Microsporum audouinii. Infection typically occurs with direct contact with the skin from the soil, animals, or the skin of other humans.

In some individual cases, the most common etiologic species is dependent on the method of transmission. Tinea corporis gladiatorum is present in athletes with extensive direct skin-to-skin contact. Patients with tinea corporis with close contact with cats or dogs commonly are infected with Microsporum canis.

The diagnosis of tinea corporis is usually clinically & is based on a thorough history and physical examination.  Testing can also be done to confirm the diagnosis.  Skin scrapings examined under a microscope with a potassium hydroxide (KOH) preparation reveal septate and branching long narrow hyphae.  However, up to 15% of cases may yield false negatives when only using KOH preparations for diagnosis.

Therefore another method for confirmation is a fungal culture.  Fungal cultures are possible but take time for definitive identification.  Cultures may begin to see growth in about five days but may take up to four weeks in certain species.  Therefore at least four weeks are needed to deem a sample as "no growth."  The most common isolation medium used for fungal cultures is a Sabourad dextrose agar.  Identification is done by examining the morphology, pigmentation, and surface topography of the culture.

Source: Treasure Island (FL): StatPearls Publishing; 2021 Jan