Superficial Fungal Infections at a Glance
- Dermatophyte species are contained in three genera: Epidermophyton, Microsporum, and Trichophyton. They are divided further according to three natural habitats (humans, animals, and soil).
- Dermatophytes infect keratinized tissue including skin, hair, and nails.
- Microscopic examination, culture, Wood's light evaluation and histopathology may all be useful in confirming a dermatophytosis.
- Trichophyton is the most common species isolated in the US.
- Several topical preparations (imidazoles and allylamine) and oral agents (griseofulvin, itraconazole, fluconazole, and terbinafine) serve as effective antifungal therapeutic options for dermatophytoses.
- Tinea nigra is a superficial dermatophyte infection that may mimic acral lentiginous melanoma.
- Piedra, which consists of white and black forms, is an asymptomatic superficial fungal infection of the hair shaft.
Mycoses are divided among three forms: (1) superficial, involving stratum corneum, hair, nails, (2) subcutaneous, involving dermis and/or subcutaneous tissue, and (3) deep/systemic, representing hematogenous spread of organisms including opportunistic pathogens in immunocompromised hosts. The focus of this chapter is the superficial mycoses and their patterns of integumentary infections (Table 188-1). A glossary of terms used in this chapter is contained in Table 188-2.
Table 188-1 Patterns of Integumentary Infections by Superficial Mycoses |Favorite Table|Download (.pdf)
Table 188-1 Patterns of Integumentary Infections by Superficial Mycoses
Table 188-2 A Glossary of Terms |Favorite Table|Download (.pdf)
Table 188-2 A Glossary of Terms
Anthropophilic—preferring humans over other animals as natural habitat
Arthroconidia—asexual spore produced by segmentation of hyphae
Dematiaceous—melanin in the cell walls of its conidia, hyphae, or both results in a darkly colored fungus
Ectothrix—dermatophyte growth pattern with spores forming a sheath on the outside of the hair shaft
Endothrix—dermatophyte growth pattern with spore formation within the hair shaft
Favus—dermatophyte growth pattern with hyphae and air spaces within the hair shaft
Geophilic—preferring the soil over humans and animals as natural habitat
Hyphae—long, filamentous fungus cells forming a branching network called mycelium
Macroconidia—asexual large multinucleate spores produced by vegetative reproduction
Microconidia—asexual small spores produced by vegetative reproduction
Zoophilic—preferring animals over humans as natural habitat
The universe of fungi comprises more than 1.5 million species worldwide. Dermatophytes (term derived from the Greek words for “skin plant”) are contained in the family of arthrodermataceae and are represented by approximately 40 species divided among the three genera: Epidermophyton, Microsporum, and Trichophyton. In the United States, Trichophyton species, and namely T. rubrum and T. interdigitale, represent the most common species isolated. Dermatophytes are classified further according to their natural habitats—humans, animals, or soil. Their ability to attach to and invade keratinized tissue of animals and humans and to utilize degradation products as nutritional sources form the molecular basis ...