Isolated congenital onychodysplasia, here referred to as nonsyndromic congenital nail disorder-7 (NDNC7), is characterized by longitudinal streaks, thinning, and impaired formation of the nail plates leading to increased vulnerability of the free nail margins. The most characteristic finding is a conspicuous reddish dome-shaped prominence of the proximal nail plate from which the longitudinal ridges originate, but this is present in only about half of patients. In most cases, all fingernails and toenails are involved, with some accentuation of the changes in the thumb nails and great toe nails (summary by Hamm et al., 2000 and Krebsova et al., 2000). For a list of other nonsyndromic congenital nail disorders and a discussion of genetic heterogeneity, see NDNC1 (161050).