Congenital bone malformations in patients with neurofibromatosis type 1 (Nf1).

To address the prevalence of congenital bone malformations in neurofibromatosis type 1 (Nf1; compared with Nf1 bone anomalies and tumors), we studied the Nf1 population of 135 children (70 boys, 65 girls) seen at the neurofibromatosis clinic, University of Catania, Italy, in the period 1990 through 1996. Twelve (8.8%) of the 135 children had congenital bone malformations: unilateral or bilateral postaxial polydactyly type A (n = 1) and type B (n = 1), bilateral postaxial polydactyly type A in association with preaxial polydactyly type 1 (n = 1) and bilateral preaxial polydactyly (n = 1); clynodactyly (n = 1); multiple segmentation anomalies of the vertebrae (n = 6), and complex costovertebral anomalies (n = 1). We found a higher frequency of polydactyly (2.9%) in comparison to that in the general population (0.014-0.12%) and in our national (0.027%) and regional (0.066%) population, and a higher frequency of vertebral (5.1%) and costovertebral (0.7%) malformations. This is the first study to state the overall prevalence of congenital bone malformations in an Nf1 population. Interestingly, polydactyly (postaxial type) and Nf1 was previously reported only once.