In each of two women, congenital aberrant hyponychia anchored to the ventral surface of the distal nail plates appeared to be the cause of paroxysmal digital pain and oblique, deep fractures of the nails.
It is postulated that the aberrant hyponychia indicate an anomaly of the developing fetal nail primordia and are analogous to the claw of lower primates.
Odom RB, Stein KM, Maibach HI. Congenital, Painful, Aberrant Hyponychium. Arch Dermatol. 1974;110(1):89-90. doi:10.1001/archderm.1974.01630070057013