ABSTRACT
BACKGROUND: Pterygium Inversum Unguis (PIU) is a wing-like extended hyponychium associated with the absence of the distal groove. Although a rare condition, it has been described with different names, confusing both the investigator and the reader. OBJECTIVE: We propose a new nomenclature based on tissue origin and pathology, to account for these conditions. 1) Congenital Aberrant Hyponychium 2) Acquired Pterygium Inversum Unguis 3) Acquired Reversible Extended Hyponychium. MAIN OBSERVATIONS: We report a case of a 19-year-old male, with epidermal pigmentation abnormalities, who had painful fingertips of both index fingers and thumbs since he was 13. He therefore let his finger nails grow very long, minimizing painful contact with the hyponychium. Removal of the aberrant hyponychium revealed glomus bodies aggregates with increased nerve fibers. Subsequently after excision of the hyponychium, his pain was resolved. SUMMARY: Congenital, transient or permanent changes in the hyponychium should be named and classified according to tissue origin to avoid nomenclature confusion.