A case of acquired idiopathic pterygium inversum unguis.

Pterygium inversum unguis (PIU) is a rare nail abnormality in which the distal nail bed adheres to the ventral surface of the nail plate, with obliteration of the distal groove. Because of the rarity of this condition, its exact origin is unknown. This disorder can be either congenital or acquired, with or without a family history. The acquired forms may be idiopathic or secondary to systemic connective tissue diseases or other causes such as stroke, neurofibromatosis, leprosy, or the use of nail fortifiers. We present an unusual case of acquired idiopathic PIU of the 10 fingernails in a 22-year-old man.