Osteopetrorickets.

Rickets is a paradoxical complication of osteopetrosis resulting from the inability of the osteoclasts to maintain a normal calcium-phosphorus balance in the extracellular fluid. Detection of rickets in a child with osteopetrosis is necessary, because treatment of the rickets with vitamin D leads to improvement in activity, decrease in irritability, improvement of appetite, and protects against recurrent respiratory tract infections. If bone marrow transplantation is feasible, then for better results, rickets should be completely treated prior to the transplantation.