Familial occurrence of the antiphospholipid syndrome.

In a family of four the whole spectrum of antiphospholipid and associated antibodies was present but without evidence of connective tissue disease. All four members had anticardiolipin antibodies; two had a confirmed lupus anticoagulant. Thrombocytopenia was severe in one and associated with a high titre of antiplatelet antibody, while another member was found to have a positive antiglobulin test. One member also had a low protein C concentration while two had decreased concentration of protein S. Factors that predispose to these antibodies may be environmental as well as genetic. In view of the well known association of spontaneous thrombotic events with some of these antibodies the prognosis for the family members must be guarded.