ACTIVATED PROTEIN-C RESISTANCE PHENOTYPE AND GENOTYPE IN PATIENTS WITH PRIMARY ANTIPHOSPHOLIPID SYNDROME

We studied both inherited and acquired activated protein C (APC) resis tance in a group of 22 patients with primary antiphospholipid syndrome (APS). The APC resistance genotype was assessed using a PCR-based ana lysis for the factor V R506Q (Leiden) mutation. One patient with prima ry APS was found to be heterozygous for the factor V Leiden mutation. He and other family members were affected by severe thrombophilia and had a familial form of primary APS. The APC resistance phenotype was a ssessed by measuring the prolongation of the activated partial thrombo plastin clotting time in response to APC. It was found in five out of six patients with APS, in one of them transiently. We have found that the APC resistance phenotype is more frequent than the genotype in pri mary APS. It would seem that patients with thrombophilia should be inv estigated for APC resistance even if found to have antiphospholipid an tibodies and/or lupus anticoagulants.