Atraumatic osteonecrosis after estrogen replacement therapy associated with low protein S level in a patient with Turner syndrome.

Atraumatic osteonecrosis has been associated with a variety of clinical conditions including corticosteroid usage, alcoholism, infections, hyperbaric events, storage disorders, marrow-infiltrating diseases, coagulation defects, and some autoimmune diseases. Osteonecrosis due to thrombophilia is an extremely rare condition with only few cases reported previously in the literature. Hormone-replacement therapies cause increased risk of venous thrombosis, probably by causing a synergistic effect with inherited clotting defects. In this article, we report a young female with Turner syndrome, who developed avascular necrosis of the femoral head during treatment with oral estrogen, which was associated with low protein S levels.