The gene for pycnodysostosis maps to human chromosome 1cen-q21.

Pycnodysostosis (OMIM 265800) is an autosomal recessive skeletal disorder first described by Maroteaux and Lamy that is characterized by short stature, increased bone density, delayed closure of cranial sutures, loss of the mandibular angle, dysplastic clavicles, dissolution of the terminal phalanges of the hands and feet, dental abnormalities and increased bone fragility. Patients have a typical appearance secondary to prominence of the calvarium, smallness of the facial features, prominent nose and micrognathia. The French painter, Henri de Toulouse Lautrec (1864-1901), is believed to have had the disorder. Although more than 100 cases have been reported, we are aware of only two large consanguinous pedigrees in which the pycnodysostosis disorder segregates. We have studied the segregation of the pycnodysostosis phenotype in a large consanguinous Mexican pedigree, the clinical features of which are very similar to those described in the Arab pedigree studied by Edelson et al. Here, we report linkage for the pycnodysostosis phenotype in the 1cen-q21 region of human chromosome 1, and discuss candidate genes for this skeletal disorder.