Fungal infections of the perionychium.

There are two types of fungi (yeasts and molds) both of which can cause superficial infections of the perionychium. Yeasts (such as Candida albicans) grow as single cells and reproduce by asexual budding. In contrast, molds grow in long filaments, called hyphae. There are approximately 100,000 species of fungi that have been characterized. Most of these are ubiquitous. Fortunately only about 200 are human pathogens, and only a handful are commonly found to be associated with human disease. This article discusses causes, symptoms, diagnosis, and treatment of the most common fungal infections of the perionychium, including superficial dermatophytosis, onychomycosis, and chronic paronychia.