Pycnodysostosis. A variant form with visceral manifestations.

The history of a 3-year-old boy is presented who has clinical and radiological features of pycnodysostosis. He also suffers from haematological and visceral complications suggestive of osteopetrosis, which have not previously been described in pycnodysostosis. This variant form of dense bone disease appears to provide the clinical link between pycnodysostosis and osteopetrosis and shows yet another example of phenotypic and perhaps genotypic heterogeneity in metabolic diseases.