Osteoporosis and osteosclerosis in sickle cell/beta-thalassemia: the role of the RANKL/osteoprotegerin axis.

Bone mineral density (BMD) was evaluated in 52 patients with HbS/beta-thalassemia. Seventeen (32%) patients had osteopenia/osteoporosis and 30 (57%) had osteosclerosis. Bone resorption was diminished in patients with osteosclerosis and increased in those with osteopenia/osteoporosis. The sRANKL/osteoprotegerin ratio was elevated in the osteosclerotic group. Osteoporosis patients had mild renal impairment and their BMD correlated with osteoprotegerin, and bone resorption markers. Osteosclerosis patients had multiple infarctions in the studied bones that led to reduced osteoclast activity and increased BMD. In conclusion, HbS/beta-thalassemia patients may develop osteopenia/osteoporosis mainly due to marrow expansion or osteosclerosis because of ischemia after a vaso-occlusive crisis. The RANKL/ osteoprotegerin axis participates in these phenomena.