MTHFR and familial avascular necrosis of femoral head: In a population of 36 patients entering a treatment trial with low-molecular-weight heparin (LMWH) for treatment of femoral head osteonecrosis they found gene polymorphisms that resulted in increased activity of the plasminogen activator inhibitor-1 gene (PAI-1), alterations in the methylenetetrahydrofolate reductase (MTHFR), and resultant hypofibrinolysis concurrent with higher homecysteine and lipoprotein levels than controls [34].