The significance of foot process effacement in immunoglobulin a nephropathy: clinicopathologic study of 161 cases with light, immunofluorescence and electron microscopic studies.

IGA nephropathy (IGAN) is the most common glomerular disease worldwide. Patients may present with hematuria and non-nephrotic (NNRP) or uncommonly nephrotic range proteinuria (NRP). To the authors' knowledge, correlation of podocyte foot process effacement (FPE) with subclasses of IGAN and proteinuria (PT) has not been studied. Retrospectively, 161 cases of IGAN with light, immunofluorescence, and electron microscopy (EM) were reviewed and classified according to Haas classification. EM was available in 110 out of 161 (67%) cases. FPE was evaluated as mild, <30%; moderate, 30–70%; and severe, >70% and was correlated with class and the level of PT. Out of 161 cases, 101 were males and 60 were females with M:F ratio of 1.71:1. In 72 cases, race was known as follows: white, 63 (88%); black, 6 (8%); Hispanic, 2 (3%); Asian, 1 (1%). Clinical history was available in 94 cases: PT 39 cases (42%), PT+hematuria 33 cases (35%), hematuria 15 cases (16%), and renal failure in 7 cases (7%). In 88 cases with FPE, PT was nephrotic in 21 and non-nephrotic in 29 cases. FPE is common in IGAN. No correlation between FPE and IGAN subclass (p=.42) or proteinuria group and IGAN subclass (p=.10) is present. Whether FPE is simply a reflection of other pathologic mechanisms and its significance in the pathophysiology of IGAN requires further investigation.