Late Presentation of Galloway-Mowat Syndrome (GAMOS) Associated With Membranous Nephropathy: A Case Report

We present a rare case of Galloway-Mowat syndrome (GAMOS) in an elderly patient with a WD repeat domain 73 (WDR73) gene deletion. A 64-year-old man with recurrent deep vein thrombosis on anticoagulation, intermittent atrial fibrillation, ulcerative colitis, apical hypertrophic cardiomyopathy, hypertension, and biopsy-proven membranous nephropathy (MN) presented with urinary frequency associated with frothing. His physical examination was unremarkable. His workup revealed worsening proteinuria, which was previously controlled with tacrolimus, low-dose steroid, and enalapril. His laboratory workup showed a serum creatinine level of 1 mg/dL, albumin at 3.5 g/dL, a urine-protein-to-creatinine ratio of 2,800 mg/g, complement 3 (C3) at 127 mg/dL, and complement 4 at 41 mg/dL. Although APOL1 testing was negative, a pathologic deletion in the WDR73 gene was identified. Repeat kidney biopsy showed MN with rare global glomerulosclerosis with mild interstitial fibrosis. Immunofluorescence showed a granular pattern along capillary walls for immunoglobulin G (IgG), C3, kappa, and lambda light chains. However, it was negative for M-type phospholipase A2 receptor (PLA2R), thrombospondin type 1 domain-containing 7A, and neural epidermal growth factor-like 1. An electron microscope showed a markedly irregular contour of the basement membrane with subepithelial and intramembranous electron-dense deposits. Our patient was diagnosed with GAMOS associated with MN, and intensive management of proteinuria was initiated. We present this unique patient with GAMOS and PLA2R-negative MN in an adult.