Activated protein C resistance in homozygous sickle cell disease.

The activated protein C resistance (APC-R) ratios in 50 patients with steady state homozygous sickle cell (SS) disease and 59 healthy AA controls was measured. There was a significant reduction in median APC-R ratio in sickle cell disease compared to controls. This reduction in APC-R ratio was not explained by (1) the presence of the factor V Leiden, found in only one of 165 patients with SS disease including those tested for APC-R, or (2) the presence of lupus anticoagulants. However, the raised levels of factor VIIIC in SS patients in this study may be contributing to increased resistance to APC, which in turn may contribute to the vaso-occlusive complications of SS disease.