Chapter 123: Tinea Corporis

Patient Story

A 6-year-old girl is brought to the office for a round, itchy rash on her body (Figure 123-1). 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 resolved in 3 to 4 weeks. The family cat was also taken to the veterinarian for treatment.

Introduction

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.

Epidemiology

Dermatophytes are the most prevalent agents causing fungal infections in the US, 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.

Etiology and Pathophysiology

Tinea corporis is caused by fungal species from any one of the following three dermatophyte genus’: 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.

Risk Factors

• Participation in daycare centers.

• 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).

Diagnosis

The diagnosis can be made from history, clinical presentation, culture, and direct microscopic observation of hyphae in infected tissue and hairs after KOH preparation.

Clinical Features

• 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 123-1).

• Central clearing is not always present (Figure 123-2).

• Although scale is the most prominent morphologic characteristic, some tinea infections will actually cause pustules from the inflammatory response (Figure 123-3).