Thirty-eight percent of probands and 19% of relatives were positive for at least one aPL, with little overlap between the different aPL studied. -No aPL-negative proband developed thrombosis. Two of the aPL-positive probands had thrombotic events before testing, and a third one showed thrombosis after testing. Only two probands had high levels of IgG aCL and showed thrombosis. The occurrence of aPL positivity in relatives was not always related to its presence in probands. None of the aPL-positive relatives had hadthrombosis, but recurrent fetal loss was noted in one aPL-positive mother with SLE. Although there was a high frequency of SLE, SLE-like disease, auto-immune disorders or positive serological findings for lupus in first-degree relatives, many of these relativew did not test positive for aPL.Conclusion
The high levels of IgG aCL may be considered a risk factor for thrombosis. Findings in relatives suggest a multifactorial origin for autoimmune disease and antibody production. Pediatrics 1993;92:849-853; systemic lupus erythematosus, antiphospholipid antibodies, anticardiolipin, lupus anticoagulant, VDRL test, relatives.