[Avascular necrosis of the bone after organ transplantation]

Avascular bone necrosis under immunosuppressive therapy is a well known sequel following solid organ transplantation. Most cases affect hip, knees or shoulders in more than one location and occur in connection with the use of high-dose steroids. In this 50 year old female immunosuppressive therapy consisted of sirolimus and mycophenolate mofetil after a renal transplantation 2 years ago. Steroids had been completely withdrawn after avascular necrosis of the femoral head. Physical examination revealed a reddened and painful left ankle. C-reactive protein was elevated while autoimmune antibodies, rheumatoid factor and screening for reactive arthritis remained negative. Joint fluid examination ruled out infection or gout. Plain radiographs were normal. Under the presumptive diagnosis of erysipelas antibiotic therapy was started, however, without success. Magnetic resonance imaging finally revealed bilateral tibial and tarsal bone necrosis as the underlying cause. In conclusion, avascular bone necrosis should remain an important differential diagnosis in patients with bone or joint pain and a history of organ transplantation, regardless of the present use of steroid therapy.