Superficial fungal infections are among the most common diseases of the skin, affecting millions worldwide. The high global prevalence and ease of communicability render such infections a public health concern.
Dermatophytosis is a general term used to describe superficial fungal infections of the skin, hair, and nails. The infectious agents, referred to as dermatophytes, are a group of closely related fungi equipped with the capacity to invade keratinized tissue of both humans and animals. Since fungi are generally incapable of penetrating deeper tissues, infections are typically restricted to the nonliving cornified layers of the hair, skin, and nails. The clinical presentation and severity of dermatophytosis varies widely according to the anatomic site of the infection, the specific dermatophyte, and the immunological defense of the host.
The clinical term “tinea” refers exclusively to dermatophyte infections. Tinea infections are classified according to their anatomic location (Table 18-1). While a single dermatophyte species can cause a variety of clinical manifestations in different parts of the body, the same clinical picture may be due to dermatophytes of different species or genera.
TABLE 18-1COMMON CUTANEOUS FUNGAL INFECTIONS ||Download (.pdf) TABLE 18-1 COMMON CUTANEOUS FUNGAL INFECTIONS
|Clinical Condition ||Site of Infection ||Common Dermatophytes |
|Tinea Capitis ||Scalp || |
|Tinea Corporis ||Trunk and extremities || |
|Tinea Cruris ||Genitalia, perineal and perianal skin∗ || |
|Tinea Pedis ||Feet || |
|Tinea Unguium (Onychomycosis) ||Nails of the hands or feet || |
Clinically relevant dermatophytes are classified into three genera, Epidermophyton, Microsporum, and Trichophyton.1 Depending on their habitat, dermatophytes are also classified as anthropophilic (human), zoophilic (animal), or geophilic (soil). Anthropophilic organisms are responsible for most human cutaneous fungal infections and rarely infect other animals. Zoophilic dermatophytes are associated with animal fungal infections but occasionally infect humans. Geophilic dermatophytes are primarily associated with keratinous materials such as hair, feathers, hooves, and horns after these materials have been dissociated from living animals and are in the process of decomposition. These species may cause human and animal infection.1 Dermatophytes are spread by direct contact from other people (anthropophilic fungi), animals (zoophilic fungi), soil (geophilic fungi), or indirectly from fomites. Fomites such as combs, towels, blankets, and pillows can disseminate fungus from a primary source to secondary contacts. However, person-to-person contact is the most common source of infection in the United States....