The frequency of IgA aCL was significantly higher in patients with APS: in 26 (49%) of 53 patients with primary APS (PAPS), in 5 (42%) of 12 with probable APS, in 35 (59%) of 59 with SLE + APS, in 9 (14%) of 63 with SLE, in none of the comparison group, and in 2 (2%) of the control one. The gene discussed is ACLY; the disease is systemic lupus erythematosus.