Onychomycosis is a prevalent and clinically relevant complication among individuals with diabetes. It is associated with an elevated risk of secondary fungal and bacterial infections, foot ulceration, and, in advanced cases, amputation. Factors contributing to the increased prevalence of onychomycosis in this population include age, peripheral vascular disease, poor glycemic control, neuropathy, suboptimal foot hygiene, and nail trauma. While dermatophytes are the most common pathogens, diabetic patients are more prone to mixed infections involving Candida species with varying antifungal susceptibility profiles, necessitating accurate identification to guide therapy. Prompt diagnosis and early intervention are important to prevent complications. Systemic antifungals such as terbinafine and itraconazole are considered first-line therapies, particularly for moderate to severe onychomycosis. However, drug interactions, renal, hepatic, and metabolic comorbidities may necessitate individualized treatment plans. For patients with mild to moderate disease, or contraindications to oral therapy, topical agents such as efinaconazole or tavaborole offer viable alternatives. Adjunctive measures, including education on foot hygiene, prompt treatment of tinea pedis, and environmental sanitization, are important in preventing recurrence and reinfection. This review summarizes the epidemiology, diagnosis, and treatment considerations for onychomycosis in diabetic patients, emphasizing the need for individualized care to improve outcomes in this high-risk population.

This retrospective case series evaluated off-label voriconazole for distal lateral subungual onychomycosis (DLSO) unresponsive to standard therapy. Twenty-nine culture-confirmed patients who had failed terbinafine (250 mg daily × 12 weeks) and itraconazole pulses (200 mg twice daily for 1 week/month × 3) received voriconazole (200 mg twice on day 1, then 200 mg daily for 3–4 months). Assessments occurred at 2, 4, 6–9, and 12 months; the primary endpoint was combined clinical cure (≥90% nail clearance) plus mycological cure (negative KOH and culture) at 12 months. Intention-to-treat included 29 patients; per-protocol included 27 (two did not complete follow-up). In the per-protocol cohort, combined cure was 55.6% (15/27) and mycological cure 74.1% (20/27). Complete clinical cure occurred in 66.7% (18/27); 25.9% (7/27) improved markedly, 3.7% (1/27) mildly, and 3.7% (1/27) showed no improvement. Voriconazole was well tolerated and may be considered for DLSO refractory to terbinafine ± itraconazole. Antifungal stewardship remains essential.