Familial antiphospholipid antibody syndrome: Criteria for disease and evidence for autosomal dominant inheritance

Objective. To develop diagnostiic criteria for a familial form of antiphospholipid antibody syndrome (APS), identify families with >1 affected member, examine possible modes of inheritance, and determine linkage to potential candidate genes. Methods. Family members of probands with primary APS were analyzed for clinical and laboratory abnormalities associated with APS. Families with ≥2 affected members were analyzed by segregation analysis and typed for candidate genetic markers. Results. Seven families were identified. Thirty of 101 family members met diagnostic criteria for APS. Segregation studies rejected both environmental and autosomal recessive models, and the data were best fit by either a dominant or codominant model. Linkage analysis showed independent segregation of APS and several candidate genes. Conclusion. Clinical and laboratory criteria are essential to identify the spectrum of disease associated with APS. We believe a set of criteria was developed that can precisely define affected family members with APS. Modeling studies utilizing these criteria strongly support a genetic basis for disease in families with APS and suggest that a susceptibility gene is inherited in an autosomal dominant pattern. However, in these families, APS was not linked with HLA, Fas, or other candidate genes, including β₂- glycoprotein I, HLA, T cell receptor β chain, Ig heavy chain, antithrombin III, Fas ligand, factor V, complement factor H, IgK, and Fas.