Retronychia of the toenails: a review with emphasis on pathogenesis, new diagnostic and management trends.

Retronychia is a condition, first described in 1999, characterized by the embedding of the proximal nail plate into the proximal nail fold and the stacking of a multiple generations of nail plates beneath the proximal nail fold. The disease affects frequently the toenails and is associated with stress-relevant situations including repetitive trauma, ischemic etiologies, postpartum, and compartment syndrome. Predisposing factors including static disorder of the feet may be underestimated. The paucity of data regarding the predisposing factors is because existing studies are limited to small case reports, case series, and retrospective studies. The diagnosis is clinical, which could be challenging because retronychia can easily mimic other nail disorders with chronic paronychia. Since the first description, significant advances have been made regarding diagnostic criteria including ultrasonography. We performed a systematic review of the literature on retronychia from inception to April 2018 with an emphasis on the pathogenesis and new diagnostic and management trends.