Congenital brachydactyly and nail hypoplasia: clue to bone-dependent nail formation.

Congenital hyponychia and anonychia are rare malformations which may form part of syndromes such as nail-patella syndrome, ectodermal dysplasias and brachydactylies, or may occur as an isolated finding. Congenital hyponychia and anonychia are frequently accompanied by underlying skeletal abnormalities. A 20-year-old woman showed congenital bilateral hypoplasia or aplasia of the second, third and fourth toenails with corresponding phalanx dysplasia or aplasia of the affected toes. Malformations of the hands or other congenital defects were absent. The findings in this patient do not exactly fit any known entities. Our clinical observation prompted us to review the literature on congenital hyponychia/anonychia and to summarize recent advances in understanding molecular events in nail development. In conclusion, the association of nail anomalies with aplasia and/or hypoplasia of corresponding middle and/or distal phalanges supports the hypothesis of bone-dependent nail formation.