Osteoblasts in the Vicinity of Osteoclasts in a Case of Infantile Osteopetrosis

An 18-month-old girl with failure to thrive, frontal bossing, bilateral proptosis, profound hepatosplenomegaly, severe anemia and thrombocytopenia was admitted to our pediatric oncology department. On physical examination she was a fussy baby with malformed teeth and abdominal distension. There was complete visual loss in the child. Laboratory data showed severe anemia, normal leukocyte counts with leukoerythroblastosis, and moderate thrombocytopenia (platelet counts 57000 /µL ). Liver transaminases were three times the normal values. Hemoglobin electrophoresis was normal. Skeletal survey showed remarkable sclerosis of the base of the skull, bone within bone appearance in vertebrae and metaphyseal fraying and cupping in distal long bones of the extremities which were all in favor of osteopetrosis. Bone marrow aspiration of the infant revealed a mild to moderate hypocellular marrow. There were increased number of osteoclasts (about 5 osteoclasts per 500 cells) observed in high power fields (×100). There were also osteoclasts with increased size and nucleation noticeable in some occasional fields (figure 1, 2). Another noticeable finding which prompted us to report this case was the simultaneous increase in the number of osteoblasts along with osteoclasts; some even close together in the same field (figure 2, 3).