Chapter 248

The skinfolds of the body include the groin, intergluteal cleft, axilla, inframammary, and pannus regions. The skinfolds have unique characteristics that set them apart from other regions of the body. For one, these areas are almost continuously occluded. As a result, scale does not develop; maceration and fissuring develop instead. This situation alters the appearance of papulosquamous diseases and inflammatory processes. The occlusion also allows for the development of a warm, moist environment favorable to the growth of fungi, yeast, and bacteria. Although many skin diseases can affect the skinfolds to some degree, this chapter focuses on common disorders where skinfold eruptions are the main finding.

An important point for treatment of intertriginous diseases is avoiding combination corticosteroid/antifungal products. Although processes in the groin folds can be confusing and complicated by secondary change, using combination products may further cloud the clinical picture. If improvement is seen, it is difficult to ascertain which medication prompted the change. And, finally, the corticosteroid component of these medications is too strong to be used in the occluded intertriginous skin, and may produce irreversible striae with long-term use.1

This chapter discusses common infections, infestations, sexually transmitted diseases, and inflammatory and reactive conditions that involve the groin and skinfolds.

### Tinea Cruris

Tinea cruris is a fungal infection of the groin commonly called “jock itch.” It is very common in males, uncommon in females, and exceedingly rare in children. Tinea cruris results from invasion of the stratum corneum by the dermatophyte types of fungi (see Box 247-2 in Chapter 247, Disorders of the Hands, Feet, and Extremities). It is transmitted via direct contact [person to person, or animal (usually kittens or puppies) to person] or fomites.

#### Clinical Features

Examination is significant for symmetric erythema with a peripheral annular slightly scaly edge (Figure 248-1). The groin is typically involved, and the process may extend onto the inner thighs and even the buttocks. The penis and scrotum are spared, a distinguishing feature of tinea cruris, as most other eruptions will affect the scrotum. Frequently, tinea pedis is also found and may be spread from the feet to the groin through putting on clothes.

###### Figure 248-1.

Tinea cruris. Note raised, sharp-edged margins. (Reproduced with permission from Wolff KL, Johnson R, Suurmond R: Fitzpatrick’s Color Atlas & Synopsis of Clinical Dermatology, 5th ed. © 2005, McGraw-Hill, New York.)

#### Diagnosis

Scraping the leading edge and performing a potassium hydroxide (KOH) examination will demonstrate branching hyphae, unless the patient has recently applied topical antifungal preparations (see Box 247-3 in Chapter 247, Disorders of the Hands, Feet, and Extremities). If a KOH examination is negative, one of the other above-mentioned disorders discussed in this chapter (Table 248.01) should be ...

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