Homozygous congenital protein C deficiency is accompanied by severe thrombophilia. Thrombotic events can be reduced in number and severity by lifelong oral anticoagulation therapy. A 4-year-old boy was first diagnosed as having severe congenital homozygous protein C deficiency during the neonatal period when purpura fulminans occurred as the first manifestation of thrombosis. From this time he had been treated with phenprocoumon (INR 3.5-4.5). During an infection of the upper respiratory tract he developed signs of a new episode of purpura fulminans (INR 2.6). Additional anticoagulation therapy with LMW heparin (Clexane) and protein C concentrate was given while the oral anticoagulation therapy was continued. On the third day of this episode the boy suffered from pain of unknown origin. MRI of the abdomen and of the pelvis revealed nontraumatic osteonecrosis of the hip joint. After a few weeks of immobilisation no special treatment was necessary. One year later he was able to walk with no problem.
Conclusion: Aseptic osteonecrosis of the hip joint is associated with a variety of disorders including vascular thrombosis and haemorrhage. Especially young children and handicapped patients with thrombophilia and pain of unknown origin are suspected to have thrombosis in atypical regions.