Histiocytic osteolysis secondary to hyperbilirubinaemia: a case report.

A 6-year-old boy with Alagille syndrome, characterised by marked hyperbilirubinaemia, presented with malunion of a pathological fracture of the femur with local bone atrophy and insufficient callus formation. During corrective osteotomy, it was noted that the femur was stained dark green, suggestive of bilirubin deposition. Histology of the resected bone revealed the presence of many histiocytes and osteoclast-like multinucleate giant cells containing bilirubin particles in the cytoplasm causing bone resorption. These findings suggest that bilirubin may activate macrophages to form osteoclast-like multinucleate giant cells, resulting in histiocytic osteolysis.