Hidden in the Absence: Clinicopathologic Insights on Kidney Diseases Associated With Selective IgA Deficiency.

Selective IgA deficiency (sIgAD) is the most common type of primary immunodeficiency. The diagnosis of sIgAD has occasionally been suggested when a complete absence of background IgA immunofluorescent staining on renal biopsies was observed, but such findings have been described in only 2 patients to date. In this study, the clinical, demographic, and renal biopsy findings of 15 patients with suspected sIgAD, based on a total lack of immunofluorescence for IgA, were collected. In our cohort, most patients presented with acute kidney injury, with or without proteinuria, and had clinical histories consistent with sIgAD, including recurrent infections, autoimmune diseases, allergic disorders, and cancer. However, only 1 patient had a known history of sIgAD. Immunoglobulin testing was available in 10 of 15 patients, 9 of whom showed findings consistent with a diagnosis of sIgAD. Renal biopsies in most patients revealed immune-related glomerular diseases, with lupus nephritis being the most common diagnosis. Recognizing the total absence of IgA staining indicative of sIgAD is important because it can be associated with recurrent infections, autoimmune diseases, allergic disorders, anaphylactic transfusion reactions, and, rarely, malignancies.