OBJECTIVE: Familial associations of the antiphospholipid antibody syndrome (APS) offer the opportunity to study genetic mechanisms of autoantibody production and disease, but are unusual. We identified a family, including identical twins and their mother, in which all members had systemic lupus erythematosus (SLE) and presented with different manifestations of the APS. METHODS: Review of case histories and clinical laboratory results, antiphospholipid antibody (aPL) studies, complement C4 protein and gene analysis, and HLA typing of family members were performed. RESULTS: Each of the 3 family members presented with a different clinical association of the APS. These various clinical presentations were closely temporally related. No particular aPL activity could be separated out that would account for the different manifestations, although the twin with thrombocytopenia and livedo reticularis had a strikingly high IgM anticardiolipin antibody level. C4A or C4B deficiencies could not be implicated in the autoimmune process. However, the mother and the twins shared the HLA haplotype that included the class II antigens DR4, DRw53, and DQw7, which has previously been associated with aPL production. CONCLUSION: This family study emphasizes the different clinical associations of aPL production in SLE. In addition to genetic influences that appear to include HLA class II antigens, the clinical presentations also suggest an environmental trigger.
OBJECTIVE: Familial associations of the antiphospholipid antibody syndrome (APS) offer the opportunity to study genetic mechanisms of autoantibody production and disease, but are unusual. We identified a family, including identical twins and their mother, in which all members had systemic lupus erythematosus (SLE) and presented with different manifestations of the APS. METHODS: Review of case histories and clinical laboratory results, antiphospholipid antibody (aPL) studies, complement C4 protein and gene analysis, and HLA typing of family members were performed. RESULTS: Each of the 3 family members presented with a different clinical association of the APS. These various clinical presentations were closely temporally related. No particular aPL activity could be separated out that would account for the different manifestations, although the twin with thrombocytopenia and livedo reticularis had a strikingly high IgM anticardiolipin antibody level. C4A or C4B deficiencies could not be implicated in the autoimmune process. However, the mother and the twins shared the HLA haplotype that included the class II antigens DR4, DRw53, and DQw7, which has previously been associated with aPL production. CONCLUSION: This family study emphasizes the different clinical associations of aPL production in SLE. In addition to genetic influences that appear to include HLA class II antigens, the clinical presentations also suggest an environmental trigger.