Koilonychia, or 'spoon nails,' is a relatively uncommon disorder in which the nails are abnormally thin and concave from side to side, with the edges turned up. Single or multiple fingers and/or toes may be involved (summary by Bumpers and Bishop, 1980). Koilonychia is referred to here as nonsyndromic congenital nail disorder-2 (NDNC2). For a list of other nonsyndromic congenital nail disorders and a discussion of genetic heterogeneity, see NDNC1 (161050). [from OMIM]