Pyknodysostosis: a report of two siblings with unusual manifestations.

We report pyknodysostosis presenting as extramedullary haematopoiesis in one of two siblings and as obstructive airway disease in the other. Visceral manifestations are rare and have been reported in only two cases in the Indian literature. They have often been mistaken for osteopetrosis, haemolytic anaemia and other osteochondrodystrophies. The cases we report illustrate that, though the physical characteristics may be similar, it is the radiological features that are typical and help establish the diagnosis.