A comparative study of onychomycosis and traumatic toenail onychodystrophy dermoscopic patterns

[[[ Background: ]]] Onychomycosis (OM) and traumatic onychodystrophy (OD) are common causes of toenail changes. A clinical diagnosis is often impossible without mycology. Dermoscopy is helpful in this setting but yet underexplored. Prospective comparative studies between OM and OD onychoscopic findings have not been previously performed. [[[ Objectives: ]]] We sought to determine distinguishing dermoscopic presentations of OM and traumatic OD. [[[ Methods: ]]] We performed a prospective, observational study including patients presenting with ≥1 toenail onychodystrophy. All underwent onychoscopy, clinical and mycological examination. Based on these results, patients received a final diagnosis of OM or OD. Dermoscopic presentations of OM and OD patients were classified in patterns and compared. [[[ Results: ]]] In all, 110 cases of OM and 82 of traumatic OD were compared. Statistical analyses revealed that the distal pulverized and the irregular spiked macular dermoscopic patterns were predictors of an OM diagnosis. The regular macular, the non-classifiable, the total and partial homogeneous background dermoscopic patterns correlated with traumatic OD diagnosis. [[[ Conclusions: ]]] We demonstrated that OM and traumatic OD have distinctive onychoscopic presentations. Dermoscopy may be an important ancillary tool to guide their differential.