Syndactyly/brachyphalangy and nail dysplasias as marker lesions for sclerosteosis

Sclerosteosis describes an autosomal recessive form of hyperostosis corticalis generalisata (MIM 239100). Sclerosteosis is primarily a disorder of osteoblast hyperactivity and metabolic abnormalities are not present. Besides generalized bone changes the presence of asymmetric cutaneous syndactyly of the index and middle fingers is characteristic. In many cases this syndactyly is associated with nail dysplasia and therefore dermatologists should recognize this clinical finding as a possible marker of this entity. We report on a 36-year-old female of Greek origin who had had finger and nail dysplasias and facial asymmetry since birth. The patient was hospitalized on the Neurology ward because of increasing spastic and ataxic gait disturbances. Physical examination revealed numerous neurological problems resulting from bony compression of nerves. Furthermore the patient had remarkably deformed fingers with hypoplasia of the second finger on both sides. The nails were dysplastic, especially on both index fingers. All laboratory results concerning metabolic diseases were normal. It has been shown that sclerosteosis is clinically and radiographically very similar to van Buchem disease. Through a genome-wide search with a highly polymorphic microsatellite the gene responsible for van Buchem disease has been mapped to 17q12-q21, and Balemans et al. (1999) assigned the locus for sclerosteosis to the same region providing genetic support for the hypothesis of allelism. Dermatologists should be able to interpret such syndactyly associated with nail deformities as a possible hint for the diagnosis of sclerosteosis in patients with hyperostotic features.