A Review of the Diagnosis and Management of Fungal Skin and Nail Infections

A Review of the Diagnosis and Management of Fungal Skin and Nail Infections D’Arcy Little, MD, CCFP, Lecturer and Academic Fellow, Department of Family and Community Medicine, University of Toronto,Toronto, ON. SKIN DISORDERS Fungal Skin Infections Normally, the dryness and regular shedding of the skin’s keratin layer prevents microbial colonization.3 However, skin trauma, irritation or maceration may provide a route of infection. Microsporum, Trichophyton and Epidermophyton species are the most common fungal causes of skin infections.1 However, nondermatophyte fungi such as Malassezia furfur in tinea (pityriasis) versicolor and Candida species, in conditions such as perleche, vulvovaginitis or balanitis, are also potential causes.1 The physical examination is often classical in patients with a dermatophytosis. The superficial skin inflammatory response is usually greater at the edge of the lesion with evidence of central clearing.1 This feature helps distinguish dermatophytoses from other papulosquamous eruptions such as psoriasis and lichen planus, which tend to be more uniform.1 However, previous topical corticosteroid use can alter this typical appearance.1 The location of the lesion is also a diagnostic clue—dermatophytoses do not cause mucosal involvement, whereas candidal infections can. There are several diagnostic methods available for dermatophyte infections. Potassium hydroxide microscopy can be used to visualize the characteristic fungal hyphae and confirm the diagnosis. Fungal culture is slow and expensive but is useful to confirm the diagnosis, especially of onychomychosis when long-term treatment is being considered. Wood’s (ultraviolet) light may be useful for diagnosing tinea (pityriasis) versicolor, which fluoresces a pale yellow-white. Most other dermatophytes in North America do not fluoresce.1