American Board of Internal Medicine (ABIM) Certification Practice Exam

What finding is expected in the electron microscopy of FSGS?

1. Immune complex deposition

2. Foot process effacement

3. Normal glomerular structure

4. Hypercellularity

The correct answer is: Foot process effacement

Foot process effacement is a hallmark finding in the electron microscopy of focal segmental glomerulosclerosis (FSGS). In this condition, the podocytes, which are specialized epithelial cells that line the glomeruli, become damaged or stressed. This leads to a flattening or effacement of their foot processes, which are critical for maintaining the filtration barrier of the kidney. As a result, this effacement alters the structure of the glomerular filtration barrier, allowing proteins to leak into the urine and leading to nephrotic syndrome. This finding is particularly significant in the context of FSGS, as it reflects the underlying pathophysiological process that distinguishes it from other types of glomerular diseases such as minimal change disease, where foot processes may appear normal on electron microscopy. Other options may reflect findings common in other types of glomerular diseases. For instance, immune complex deposition is typically seen in conditions like membranous nephropathy or lupus nephritis, while normal glomerular structure would not be expected in a disease process. Hypercellularity pertains to glomerular hypercellularity seen in conditions like diffuse glomerulosclerosis, which is also not characteristic of FSGS.