Prevalence of antiphospholipid antibodies in nephropathies not due to systemic lupus erythematosus

Renal involvement by some types of thrombotic microangiopathy has been associated with the presence of antiphospholipid antibodies in both patients with systemic lupus erythematosus (SLE) and in those with other types of connective tissue disorders. To assess the prevalence and clinical significance of these antibodies in renal disease we prospectively studied anticardiolipin antibodies and lupus anticoagulant activity in 138 patients. These patients were classified into four groups: chronic glomerulonephritis (n = 57), acute and non-SLE systemic nephropathies (n = 13), non-immune-related nephropathies (n = 39), and SLE nephropathies (n = 29). The prevalence of antiphospholipid antibodies in patients with chronic primary glomerulonephritis (9%) was lower than in the SLE group (34%) and higher, but not significantly, than in patients with non-immunologically mediated renal diseases (2.6%). Positive patients in this group correspond to atypical "lupus-like" SLE forms or sporadic cases. In the group of patients with acute nephropathy and non-SLE systemic disorders, lupus anticoagulant was present in sic and anticardiolipin was present in four. In most cases the finding was transient and probably related to concomitant infection or active immune response. We conclude that there is a low prevalence of antiphospholipid antibodies in primary chronic glomerulonephritides, similar to that found in non-immunologically based nephropathies. The presence of these antibodies associated with chronic glomerulonephritis should raise the suspicion of SLE. On the other hand, positivity of these antibodies is a frequent finding in acute and systemic nephropathies. Therefore, the clinical and prognostic significance of their presence in these disorders should be further studied in a larger series of patients.