Onychomycosis: Diagnosis and management

Onychomycosis is a common nail ailment associated with significant physical and psychological morbidity. Increased prevalence in the recent years is attributed to enhanced longevity, comorbid conditions such as diabetes, avid sports participation, and emergence of HIV. Dermatophytes are the most commonly implicated etiologic agents, particularly Trichophyton rubrum and Trichophyton mentagrophytes var. interdigitale, followed by Candida species and non dermatophytic molds (NDMs). Several clinical variants have been recognized. Candida onychomycosis affects fingernails more often and is accompanied by paronychia. NDM molds should be suspected in patients with history of trauma and associated periungual inflammation. Diagnosis is primarily based upon KOH examination, culture and histopathological examinations of nail clippings and nail biopsy. Adequate and appropriate sample collection is vital to pinpoint the exact etiological fungus. Various improvisations have been adopted to improve the fungal isolation. Culture is the gold standard, while histopathology is often performed to diagnose and differentiate onychomycosis from other nail disorders such as psoriasis and lichen planus. Though rarely used, DNA-based methods are effective for identifying mixed infections and quantification of fungal load. Various treatment modalities including topical, systemic and surgical have been used. Topically, drugs (ciclopirox and amorolfine nail lacquers) are delivered through specialized transungual drug delivery systems ensuring high concentration and prolonged contact. Commonly used oral therapeutic agents include terbinafine, fluconazole, and itraconazole. Terbinafine and itraconazole are given as continuous as well as intermittent regimes. Continuous terbinafine appears to be the most effective regime for dermatophyte onychomycosis. Despite good therapeutic response to newer modalities, long-term outcome is unsatisfactory due to therapeutic failure, relapse, and reinfection. To combat the poor response, newer strategies such as combination, sequential, and supplementary therapies have been suggested. In the end, treatment of special populations such as diabetic, elderly, and children is outlined.