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Dermatophytes

Dermatophytes are molds that infect keratinized tissues including skin, hair, and nails. Whereas 40 dermatophyte species are known to infect humans, only about 15 of these are common causes of disease. These organisms belong to three genera, Microsporum, Trichophyton, and Epidermophyton. Because these fungi have such similar infectivity, morphology, and pathogenicity, they are often categorized according to the clinical syndrome and the preferred anatomic site with which they are associated, such as tinea capitis, tinea pedis, etc.

Fusarium, Penicillium, Paracoccidioides, & Agents of Chromomycosis

Fusarium spp. is an emerging fungal pathogen. Although long recognized as a cause of local infection involving nails, traumatized skin, or the cornea (eg, in contact lens wearers), deep or disseminated infection was not described until the mid 1970s. Despite its worldwide distribution and its frequent recovery from soil and vegetative material, infection is quite rare. Only ~ 100 cases involving invasive disease in immunosuppressed patients have been described in the medical literature.

Chromomycosis

Chromomycosis, also known as chromoblastomycosis, is a chronic subcutaneous infection caused by several different fungi. Although rarely seen in the United States, it is common worldwide. Chromomycosis occurs worldwide but is most frequently encountered in tropical and subtropical regions. The most common occurrence is in barefoot individuals, particularly among agricultural workers.

Management of Tinea Unguium

Fungal infection of the nails (onychomycosis) may be caused by a number of dermatophytes as well as by a number of other moulds and Candida species. There is wide geographical and racial variation in the causative agents, but in the UK 85-90% of nail infections are due to dermatophytes and about 5% are due to non-dermatophyte moulds.

Management of Tinea Manuum

The anthropophilic dermatophytes E. floccosum, T. mentagrophytes var. interdigitate and T. rubrutn are the most common causes of tinea manuum. Less commonly, the condition is caused by zoophilic dermatophytes, such as M. canis and T. verrucosum, or geophilic dermatophytes, such as M. gypseum. Hand infection may be acquired as a result of contact with another person, with an animal, or with soil, either through direct contact, or via a contaminated object such as a towel or gardening tool. Autoinoculation from another site of infection can also occur.

Management of Tinea Pedis

The term tinea pedis is used to refer to dermatophyte infections of the feet. These infections often involve the interdigital spaces, but chronic diffuse desquamation can affect the entire sole. The anthropophilic dermatophytes E. floccosum, T. mentagrophytes var. interdigitale and T. rubrutn are the commonest causes of tinea pedis in the UK and North America.

Management of Tinea Cruris

The dermatophytes most often encountered in tinea cruris are E. floccosum and T. rubrum. Maceration and occlusion of the skin in the groin give rise to warm moist conditions that favour the development of the infection. Tinea cruris is a common form of dermatophytosis.

Management of Tinea Corporis

Tinea corporis is caused by E. floccosum and many species of Trichophyton and Microsporum. Infection with anthropophilic species, such as E. floccosum or T. rubrum often follows autoinoculation from another infected body site, such as the feet. Tinea corporis caused by T. tonsurans is sometimes seen in children with tinea capitis and their close contacts. Tinea corporis commonly occurs following contact with infected household pets or farm animals, but occasional cases result from contact with wild mammals or contaminated soil.

Management of Tinea Capitis

The condition is worldwide in distribution, but is most prevalent in Africa, Asia and southern and eastern Europe, where it is the most common form of dermatophytosis. Improved standards of hygiene and prompt eradication of sporadic infection have led to a marked decline in the incidence of tinea capitis in North America and western Europe.