Retronychia refers to the proximal ingrowth of the nail into the proximal nail fold, typically resulting from trauma-induced disruption of longitudinal growth [1]. Normally, nail trauma results in the complete separation of the old nail plate from the matrix and nail bed [2]. A new nail plate subsequently grows beneath the old nail plate, advancing the old plate distally. For retronychia, an acute or repeated trauma results in partial separation of the old nail plate from the matrix and nail bed. Because the old nail plate is still partially attached, the new nail plate does not grow distally and instead grows underneath the old plate, pushing it upwards [3–5]. This process repeats, resulting in the layering of nail plates [2].