Sulphur Nuggets: A Distinct Dermoscopic Feature of Onychomycosis

Background: Dermoscopy is a new method to diagnose and manage nail disorders. The definite dermoscopic finding for onychomycosis, however, is still debatable. Objective: To identify the dermoscopic features that help differentiate between onychomycosis (OM) and traumatic onychodystrophy (TOD). Methods: A prospective study of 65 patients with toenail abnormalities was conducted. The patients were classified into OM and TOD groups using mycological tests (potassium hydroxide test, fungal culture, and histological examination). OM was diagnosed from positive results for all tests, while TOD was decided based on negative results for all tests and evidence of foot trauma. Dermoscopic features were recorded and compared between the two groups. Results: Most patients of the 65 patients were female (72.3%), and had a mean age of 67.9 years. Twenty-seven patients (41.5%) were diagnosed with OM, all of which were distal and lateral subungual onychomycosis. TOD, on the other hand, was determined in 38 patients. Dermoscopic findings revealed that the yellow, clumping, sulphur-nugget-like debris in the ruin appearance was significantly associated with onychomycosis (p = 0.002), while ruin appearance without sulphur nugget was not statistically correlated with onychomycosis (p = 0.068). Conclusion: The presence of sulphur nuggets in the ruin appearance is a new and helpful dermoscopic feature for onychomycosis diagnosis.