IgA nephropathy: a rare lesion in systemic lupus erythematosus.

We describe three patients with a well-established clinical diagnosis of systemic lupus erythematosus in whom the renal biopsy lesion unexpectedly is diagnostic of IgA nephropathy, not superimposed with any features of lupus nephritis. Whereas the clinical presentation and follow-up of renal disease in these patients indicate a relatively indolent course, the extrarenal manifestations of systemic lupus erythematosys have been relatively severe, and one patient died of systemic infection. IgA nephropathy hitherto has not been described in patients with systemic lupus erythematosus, and such an observation stresses that atypical glomerular lesions in these patients should raise the possibility of a nonlupus glomerulopathy.