Onychomykose

Onychomykose, or onychomycosis, is a fungal infection of the nails, most commonly affecting toenails. It is typically caused by dermatophyte fungi, especially Trichophyton rubrum and Trichophyton interdigitale, but non-dermatophyte molds and Candida species can also be involved. The infection leads to nail plate thickening, color changes (often yellow or brown), altered nail shape, subungual hyperkeratosis, and sometimes separation of the nail from the nail bed in advanced cases.

Clinically, affected nails may become brittle, crumbly, and deformed. Toenail involvement is more common than fingernail involvement and can progress slowly over months or years. The infection can be asymptomatic or cause discomfort, particularly when the nail becomes thick and hard to trim. It may occur as a superficial involvement of the nail plate or deeper invasion of the nail bed and matrix.

Diagnosis is usually clinical but should be confirmed by laboratory testing. Methods include microscopy of nail clippings with potassium hydroxide preparation and fungal culture. More recently, PCR-based assays can aid in detection. Differential diagnosis includes psoriasis, lichen planus, trauma, and other nail dystrophies.

Treatment depends on severity and location. Topical antifungals (such as ciclopirox, efinaconazole, or tavaborole) are used for milder cases or fingernail involvement but require long treatment courses. Systemic antifungals (notably terbinafine or itraconazole) are often more effective for toenail infections and require monitoring for potential side effects. Duration generally spans several months. In some cases, laser therapy or surgical nail removal may be considered. Prevention focuses on foot hygiene, treating athlete’s foot, avoiding sharing nail tools, and keeping nails trimmed and dry. Recurrence is common, even after successful treatment.