American Board of Internal Medicine (ABIM) Certification Practice Exam

Which nephrotic syndrome is characterized by a diffuse thickening of the glomerular capillary wall?

1. Focal Segmental Glomerulosclerosis

2. Membranous Nephropathy

3. Minimal Change Disease

4. Amyloidosis

The correct answer is: Membranous Nephropathy

Membranous nephropathy is characterized by a diffuse thickening of the glomerular capillary wall, which is a hallmark of this condition. In this nephrotic syndrome, the thickening results from the accumulation of immune complex deposits along the subepithelial side of the glomerular basement membrane. This alteration leads to a disruption in normal glomerular function, causing significant proteinuria, commonly seen in patients with nephrotic syndrome. The thickening of the capillary wall in membranous nephropathy can be visualized under electron microscopy, where one can observe a "spike" appearance on the epithelial side of the basement membrane due to the protrusion of the membrane material where the immune complexes deposit. This structural change distinguishes it from other forms of nephrotic syndromes, which have different pathological features. In contrast, other nephrotic syndromes like focal segmental glomerulosclerosis involve focal and segmental areas of scarring in the glomeruli, minimal change disease primarily exhibits normal-appearing glomeruli with effacement of podocyte foot processes, and amyloidosis features deposits of amyloid protein leading to various architectural changes in the kidney that do not specifically result in diffuse thickening of