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 ... 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).
Hellier (1950) reported a family in which 14 individuals over 4 generations had koilonychia. The proband was a 73-year-old man who did not complain of his nails but was observed to have marked koilonychia of all the nails ... Hellier (1950) reported a family in which 14 individuals over 4 generations had koilonychia. The proband was a 73-year-old man who did not complain of his nails but was observed to have marked koilonychia of all the nails of both hands and feet. His grandson later presented because the nails of his great toes were so concave that they caught in his shoes and caused difficulty walking. The affected mother stated that she had never had to cut her nails her entire life. In all 14 affected individuals in this family, koilonychia was present in both hands and feet, and tended to be more marked on the thumbs and index and middle fingers. Apart from eczema in the proband, there were no skin abnormalities in the family. Bergeson and Stone (1967) described a 4-generation family in which 12 members had varying degrees of spooning of the nails. There were no known familial systemic diseases or associated congenital ectodermal or orthopedic defects in the family. The proband was a 20-year-old man with bilateral spooning of the nails of the thumbs, index fingers, and great toes. Of the 12 affected individuals, 7 had spooning of the thumb nails only and 5 had involvement of the thumb, index, and great toe nails. As in the family reported by Hellier (1950), this pedigree suggested high penetrance of a dominant gene, with varying expressivity regarding degree of nail involvement, affecting males and females alike. Schleutermann et al. (1970) reported a 5-generation pedigree in which 8 individuals had varying degrees of koilonychia ('hollow nails'). The proband, her mother, and 2 maternal uncles had marked concavity of all fingernails with the most severe abnormality in the thumbnails, which also showed longitudinal ridges; the nails of the great toes were also concave. The proband's daughter was more mildly affected, having flat fingernails that appeared thin, with thumbnails that were only mildly concave, and the nails of her smaller toes appeared normal. No abnormality other than that of the nails was detected in the kindred, and the pedigree was consistent with autosomal dominant inheritance. Char (1971) described a family of Lumbee Indian descent, in which 8 individuals over 4 generations had koilonychia. The proband was a 29-year-old man in whom the nails of all digits were spoon-shaped, with the fingers being more severely affected than the toes. The nails were firm and slightly thicker than normal. His teeth were normal and he had no cataracts. Bumpers and Bishop (1980) reported a pedigree in which 16 affected individuals over 4 generations had koilonychia of all fingernails and toenails. The proband was a 13-year-old boy who had notable concavity of all his nails, with the most exaggerated concavity expressed bilaterally in the nails of his thumbs and great toes. He was otherwise in good health, with no orthopedic or ectodermal abnormalities. His mother and sister were examined and found to have identical nail changes. The phenotype was first noted in the proband's great-grandfather, whose parents and 6 sibs were all unaffected, suggesting that the trait began as a new dominant mutation in that individual; examination of the pedigree indicated a high degree of penetrance.