Identification of selective immunoglobulin a deficiency by renal biopsy.

We report three cases of selective immunoglobulin A (IgA) deficiency in which lack of direct immunofluorescent staining for IgA on renal biopsy specimens contributed to the diagnosis. In two patients, one with systemic lupus erythematosus and the other having asthma with nephrotic syndrome, the diagnosis of IgA deficiency was suggested by the complete absence of IgA on the renal biopsy. In the third patient, a renal transplant recipient, initial biopsies demonstrated donor-derived IgA, which disappeared on subsequent biopsies. The diagnosis of IgA deficiency was confirmed in all three patients by serologic quantification of IgA.