Bone growth and haemopoiesis: steroid reversible anaemia, myelofibrosis and increased bone formation in a child.

Factors regulating the interaction between bone marrow haemopoietic cells, stromal elements and bone growth are poorly understood. Disturbance in the equilibrium between these elements can occur as the result of metabolic bone disease, haematologic disorders, neoplasia and infections. The present report concerns a child with myelofibrosis, hypoplastic/dyserythropoietic anaemia, osteoblast proliferation and increased bone formation. A positive tuberculin skin test and elevated EB virus titre indicated previous exposure to Mycobacterium tuberculosis and Epstein-Barr virus. No active focus of infection was identified and no improvement occurred following anti-tuberculous therapy. A dramatic improvement occurred on corticosteroid therapy. Reticulocytosis was followed by an increase in haemoglobin and platelets and a decrease in ESR. Bone marrow fibrosis resolved and the marrow was repopulated with normal haemopoietic tissue. The bone abnormalities improved both radiologically and histomorphometrically. Relapse occurred when steroids were discontinued. Bone marrow tissue culture supernate from the patient during the active phase of the disease inhibited colony formation by normal marrow mononuclear cells. This was reversed by steroid therapy. It is postulated that EB virus may have triggered osteoblast proliferation with resultant bony and haematologic changes. Response to corticosteroids could be explained on the basis of suppression of osteoblast activity and correction of fibroblast mediated suppression of haemopoiesis.