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. This chapter discusses common infections, infestations, and inflammatory and reactive conditions that involve the groin and skinfolds. Sexually transmitted infections are discussed in chapter 149. Molluscum contagiosum is discussed in chapter 251.
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
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 Table 253-4). It is transmitted via direct contact (person to person, or animal [usually kittens or puppies] to person) or fomites.
Examination is significant for symmetric erythema with a peripheral annular slightly scaly edge (Figure 252-1). The groin is typically involved, and the process may extend onto the inner thighs and even the buttocks. The penis and scrotum are typically spared, a distinguishing feature of tinea cruris because most other eruptions will affect the scrotum. Frequently, tinea pedis is also found and the dermatophyte infection may be spread from the feet to the groin through putting on clothes.
Tinea cruris. Note raised, sharp-edged margins. [Photo contributed by University of North Carolina Department of Dermatology.]
Scraping the leading edge and performing a potassium hydroxide examination (see Table 252-6) will demonstrate branching hyphae (see Figure 252-1), unless the patient has recently applied topical antifungal preparations. If a potassium hydroxide examination is negative, consider one of the other disorders discussed in this chapter (Table 252-1).
TABLE 252-1Inflammatory Disorders of the Skinfolds