Congenital absence of the nails is a rare condition. Some pedigrees display complete congenital absence of the nails (see, e.g., NDNC4, 206800), whereas in other pedigrees there is only partial congenital anonychia, with the thumbs and great toes ... Congenital absence of the nails is a rare condition. Some pedigrees display complete congenital absence of the nails (see, e.g., NDNC4, 206800), whereas in other pedigrees there is only partial congenital anonychia, with the thumbs and great toes most severely affected and progressively less severe changes in the more lateral digits (summary by Charteris, 1918). This form of nail disorder is referred to here as nonsyndromic congenital nail disorder-6 (NDNC6). For a list of other nonsyndromic congenital nail disorders and a discussion of genetic heterogeneity, see NDNC1 (161050).
Charteris (1918) described a 34-year-old man in whom nails of the thumbs, second, and third fingers were entirely absent, with development of only the ulnar half of the nails of the fourth fingers and completely normal nails on ... Charteris (1918) described a 34-year-old man in whom nails of the thumbs, second, and third fingers were entirely absent, with development of only the ulnar half of the nails of the fourth fingers and completely normal nails on the fifth fingers. A similar condition was present in his feet, where the three inner toes lacked nails and the fourth toe had a rudimentary nail, whereas the fifth toe had a normal nail. Charteris (1918) observed that whereas the fingers showed no indication of any attempt at nail formation, in the toes there were distinct grooves indicating the nail beds. The defect could be traced back 3 generations, to the patient's great-grandmother; and 2 of his 4 children had the same abnormality of the nails whereas the other 2 had normal nails. Hobbs (1935) reported a 29-year-old man with a 'peculiar distribution of the nail substances,' in which the nail deficiency was most marked on the thumbs and great toes, but there were no normal nails. He had no abnormalities of hair, teeth, or skin, and the patellae were normal in size and position. X-rays showed that the distal phalanges of his hands and feet were tapered and spatulated. A female cousin displayed the same nail dystrophy. Family history by questionnaire revealed that the nail dystrophy extended over 4 generations of the family, although the changes noted by the 11 affected individuals varied considerably. No other ectodermal abnormality or skeletal deformities were noted. Hobbs (1935) stated that because many reported patients with nail dystrophy did not have x-rays taken, anomalies of the osseous system had undoubtedly been missed. Strandskov (1939) described a young woman who had bilateral absent thumbnails, with normal development and demarcation of the nail beds but no cornification. The remainder of her fingers had nails with varying degrees of abnormality: both index fingers had thin nails that were reported to grow very little, and her other nails had unusually large and pointed lunulae. Her hands were noted to be short, apparently due to short phalanges as well as short metacarpals; in addition, the distal joints of her ring fingers could be flexed only a few degrees. Her mother, a sister, and a nephew were also affected, with thin to no thumbnails and large and pointed lunulae on the remaining fingers. Strandskov (1939) noted similarities between the nail phenotype of these patients and those of Osterreicher (1929); however, affected individuals in the latter pedigree who lacked thumbnails also tended to lack patellae (see nail-patella syndrome, 161200), whereas Strandskov (1939) stated that 'this does not appear to hold true for the affected members of the present pedigree.' Absent thumbnails in female members of 3 generations of a family proved on further study to represent the nail-patella syndrome (161200) (Schleutermann, 1968). Timerman et al. (1969) described 3 of 5 affected members of a 4-generation family with anonychia and onychodystrophy. The grandfather had bilateral complete anonychia of the thumb, index, and middle fingers, with nail bed vestiges present as small ridges on the outer finger edges; his fourth and fifth fingers showed the absence of nails in the central part, with 2 small atrophied nail lamellae on the sides. In his feet, there was bilateral total anonychia of the big toes, a rudimentary ridge on the right second toe, thin narrow nail lamellae on the left second and third toes, and hypoplastic nails on the third and fourth toes. His daughter had nail rudiments that were nearly punctiform on both thumbs, with bilateral total anonychia of the second digits and left third digit, which had small sunken areas on the sides, corresponding to the nail edge. Hypoplastic nails were present on both fourth fingers, whereas her fifth fingers had normal nails. Her feet showed total absence of nails and nail beds on the right first and second toes and hypoplasia of all other toenails, with the degree of hypoplasia decreasing laterally. The daughter had an affected son, otherwise healthy, who had similar nail changes. In all 3 patients, the terminal phalanges of the first, second, and third toes had a bulging appearance. Patellae were normal by x-ray. Ahlgren et al. (1988) reported a Saudi family in which 8 individuals over 4 generations had nail dysplasia. The proband was a 2-year-old boy who presented for evaluation of bilateral congenital hip dislocation and was noted to have abnormal nails on 4 fingers and toes of each hand and foot. The changes had been present since birth and involved nails that were small in length and width and had an upper convex surface; none of the affected nails reached the fingertips. The affected nails had nail folds, and the changes were symmetric. All 3 affected sibs in the fourth generation had congenital hip dislocation, as did another sib who had normal nails. Their mother and 4 other affected relatives from the previous 3 generations had nail abnormalities, but no other relatives had hip dislocation.