Familial form of pyknodysostosis with hematologic manifestations in a child

Pyknodysostosis is characterized by post-natal onset of short-limbed short stature and generalized hyperostosis. It must be differentiated from osteopetrosis with precocious manifestations in which hyperostosis may crowd the marrow cavity with extramedullary hematopoiesis. A boy, born from consanguineous parents presented with classical features of pyknodysostosis: short-limbed stature, large skull, frontal bossing, wide anterior fontanelle and tendency to fracture. His sister had the same features at the age of 3 months; she had hepatosplenomegaly at the age of 5 months with anemia, erythroblastosis (13%), myelemia and, at 10 months, thrombocytopenia. Hyperosostis can be complicated by development of such severe hematological manifestations as classically seen in osteopetrosis. Differential diagnosis between both entities is based upon radioclinical investigation.