PURPOSE: We sought to evaluate the clinical and serologic associations with, and outcomes of, autoimmune hemolytic anemia, as compared with other types of anemia, in patients with systemic lupus erythematosus (SLE).

SUBJECTS AND METHODS: We studied 41 consecutive patients with SLE with clinically manifest autoimmune hemolytic anemia, including 27 (66%) in whom hemolysis was the initial disease manifestation. We matched each patient for age and disease duration with a patient with SLE with anemia resulting from a different cause.

RESULTS: The 41 patients had a total of 50 episodes of autoimmune hemolytic anemia. The recurrence rate was 4 per 100 person-years. Cases and controls had similar mean (± SD) lupus activity indexes (2.1 ± 1.5 vs 2.4 ± 1.3, P = 0.5). Patients with autoimmune hemolytic anemia at any time could be distinguished from patients with other causes of anemia, because they were more likely to have elevated titers of IgG anticardiolipin antibodies [odds ratio (OR) = 5.8; 95% confidence interval (CI), 1.4 to 24] and thrombosis (OR = 4.6; 95% CI, 1.0 to 21). Autoimmune hemolytic anemia at the onset of SLE was independently associated with renal involvement (OR = 5.4; 95% CI, 1.0 to 28), thrombocytopenia (OR = 7.3; 95% CI, 1.1 to 48), and possibly thrombotic episodes during follow-up (OR = 11; 95% CI, 0.8 to 160) when compared with controls with other types of anemia at the onset of SLE.

CONCLUSIONS: Autoimmune hemolytic anemia usually occurs at the onset of SLE, and its recurrence rate is low among treated patients. The association with IgG anticardiolipin antibodies and thrombosis suggests that the occurrence of autoimmune hemolytic anemia may define a subgroup of patients with SLE who have characteristic serologic and clinical manifestations.