A 6-year-old girl is brought to the office for a round, itchy rash on her body (Figure 138-1). It was first noted 2 weeks ago. The family cat does have some patches of hair loss. Note the concentric rings with scaling, erythema, and central sparing. UV light showed green fluorescence (Microsporum species) and the KOH is positive for branching and septate hyphae. The child was treated with a topical antifungal cream bid and the tinea resolves in 3 to 4 weeks. The family cat was taken to the veterinarian for treatment, too.
Tinea corporis on the shoulder of this young girl. This is a very typical annular pattern and the cat on a sweatshirt might be a clue to an infected pet at home spreading a Microsporum dermatophyte to its owner. Note the concentric rings with scaling, erythema, and central sparing. (Courtesy of Richard P. Usatine, MD.)
Tinea corporis is a common superficial fungal infection of the body, characterized by well-demarcated, annular lesions with central clearing, erythema, and scaling of the periphery.
Dermatophytes are the most prevalent agents causing fungal infections in the United States, with Trichophyton rubrum causing the majority of cases of tinea corporis, tinea cruris, tinea manuum, and tinea pedis.
- Excessive heat and humidity make a good environment for fungal growth.
- Dermatophytes are spread by exposure to infected animals or persons and contact with contaminated items.
Tinea corporus is caused by fungal species from any one of the following three dermatophyte genus's: Trichophyton, Microsporum, and Epidermophyton. T. rubrum is the most common causative agent of tinea corporis.
- Dermatophytes produce enzymes such as keratinase that penetrate keratinized tissue. Their hyphae invade the stratum corneum and keratin and spread centrifugally outward.
- Participation in daycare centers.
- Living in a nursing home.
- Poor personal hygiene.
- Living conditions with poor sanitation.
- Warm, humid environments.
- Conditions that cause weakening of the immune system (e.g., AIDS, cancer, organ transplantation, diabetes).
The diagnosis can be made from history, clinical presentation, culture, and direct microscopic observation of hyphae in infected tissue and hairs after KOH preparation.
- Pruritus of affected area.
- Well-demarcated, annular lesions with central clearing, erythema, and scaling of the periphery. Concentric rings are highly specific (80%) for tinea infections (Figure 138-1).
- Central clearing is not always present (Figure 138-2).
- Although scale is the most prominent morphologic characteristic, some tinea infections will actually cause pustules from the inflammatory response (Figure 138-3).
Tinea faciei in a young girl. There is no central clearing or annular pattern here but the KOH preparation was positive for ...