A 45-year-old patient had an acquired abnormality in which the distal part of the nail bed remained adherent to the ventral surface of the nail plate eliminating, thereby, the distal groove. The disorder was not familial; it seems to have arisen spontaneously and gradually, involving several symmetrical fingers. There were no nail plate alterations and the soft periunguinal tissues were normal.
For this pathologic entity we suggest the term "pterygium inversum unguis". A possible explanation for this nail bed abnormality is that it represents an acquired reversion, without an apparent cause, to a more primitive type of structure.
Caputo R, Prandi G. Pterygium Inversum Unguis. Arch Dermatol. 1973;108(6):817-818. doi:10.1001/archderm.1973.01620270039009