nondermatophytic

Nondermatophytic is an adjectival term used in medical mycology to describe fungi that are not dermatophytes. In clinical practice it is applied when a fungal infection of the skin, nails, or hair is caused by organisms outside the dermatophyte genera Trichophyton, Microsporum, and Epidermophyton. The designation is most commonly encountered in discussions of onychomycosis and other superficial mycoses, where cultures yield nondermatophytic fungi.

Common nondermatophytic etiologies include yeasts such as Candida species and molds such as Fusarium, Aspergillus, Scopulariopsis, and Alternaria. Distinguishing a true pathogen from a colonizer or contaminant can be challenging; diagnosis typically relies on direct microscopy and culture, with repeated positive isolation from the same site supporting a causative role. Histopathology or quantitative culture can help establish tissue invasion or significant fungal burden.

Clinical implications and management vary by organism. Nondermatophytic infections may respond differently to standard antifungal regimens used for dermatophytes, and some nondermatophyte molds show resistance to common agents. Treatment is often longer and tailored to the identified organism, and may include systemic antifungals or combination approaches, along with debridement in nail disease. Accurate identification is important for prognosis and therapy.

See also: onychomycosis, dermatophyte, mycosis.