Onychomycosis: a review

Onychomycosis is a fungal infection of the nail, causing discoloration and thickening of the affected nail plate, and is the most common nail infection worldwide. Onychomycosis was initially thought to be predominantly caused by dermatophytes; however, new research has revealed that mixed infections and those caused by non-dermatophyte moulds (NDMs) are more prevalent than previously thought, especially in warmer climates. Microscopy and fungal culture are the gold standard techniques for onychomycosis diagnosis, but high false-negative rates have pushed for more accurate methods, such as histology and PCR. As NDMs are skin and laboratory contaminants, their presence as an infectious agent requires multiple confirmations and repeated sampling. There are several treatment options available, including oral antifungals, topicals and devices. Oral antifungals have higher cure rates and shorter treatment periods than topical treatments, but have adverse side effects such as hepatotoxicity and drug interactions. Terbinafine, itraconazole and fluconazole are most commonly used, with new oral antifungals such as fosravuconazole being evaluated. Topical treatments, such as efinaconazole, tavaborole, ciclopirox and amorolfine have less serious side effects, but also have generally lower cure rates and much longer treatment regimens. New topical formulations are being investigated as faster-acting alternatives to the currently available topical treatments. Devices such as lasers have shown promise in improving the cosmetic appearance of the nail, but due to a high variation of study methods and definitions of cure, their effectiveness for onychomycosis has yet to be sufficiently proven. Recurrence rates for onychomycosis are high; once infected, patients should seek medical treatment as soon as possible and sanitize their shoes and socks. Prophylactic application of topicals and avoiding walking barefoot in public places may help prevent recurrence.