Tinea Corporis (TC) is a cutaneous fungal infection (superfical dermatophyte) that is also referred to as Tinea Circinata in the medical literature. It is commonly known as ringworm although a worm has nothing to do with it. TC includes all fungal skin infections except those involving the scalp (tinea capitis), beard (tinea barbae), face (tinea faciei), hands, feet (tinea pedis) and groin (tinea cruris). The lesions are characterized by one or more circular, sharply circumscribed, slightly erythematous, dry, scaly, usually hypopigmented plaques.
Progressive central clearing produces annular outlines that give them the name “ringworm.” Lesions may widen to form rings, many centimeters in diameter, as shown on the first image above… In the United States, Tinea rubrum (T. rubrum), Microsporum canis (M. canis), and Tinea mentagrophytes (T. mentagrophytes) are the most common fungal organisms, although any of the dermatophytes can cause skin infections. M. canis is often found as crusty lesions on the nose, paws/nails, skin and fur of dogs and is not infrequently transmitted to humans that are in close proximity. M. mentagrophytes is found in Southeast Asian bamboo rats and can cause widespread epidemics of highly inflammatory TC.
DIAGNOSIS: For dermatologist the diagnosis is relatively easy to make by finding the fungus under the microscope on a scraping. The scrapings can also be cultured on a medium such as DTM, demonstrating growth within 1-2 weeks.
DIFFERENTIAL DIAGNOSIS: The most frequent condition confused with TC is nummular eczema (click HERE), particularly in desert environments such as we have here in Las Vegas. Other conditions that may be confused with TC include pityriasis rosea (click HERE), impetigo, secondary and tertiary syphilis (click HERE), seborrheic dermatitis (click HERE), and psoriasis (click HERE).
TREATMENT: Topical treatment with antifungal medications (lotrimin, lamisil, miconazole) for TC is often very effective and there are many over the counter preparations available. If you have pets be sure to have your veterinarian check your dogs for possible infections around the nose, nails, skin and fur (click HERE). If you aren’t sure if you have TC you should see a dermatologist to sort it out. Extensive disease or fungal folliculitis requires systemic antifungal treatment. To read more about TC click HERE and HERE.