A 43-year-old man comes to the office due to shortness of breath and fatigue. Over the last 2 weeks, his fatigue has been so profound that he has "little energy, even to get out of bed." The patient has no chills but has experienced recent weight gain and ankle swelling. He has no prior medical conditions and takes no medications. Blood pressure is 168/94 mm Hg, and pulse is 95/min and regular. The patient has bilateral lower extremity pitting edema limited to the ankles. Urinalysis reveals 2+ protein, white blood cell count of 5-7/hpf, and red blood cell count of 75-100/hpf. He undergoes a kidney biopsy; immunofluorescent microscopy findings are shown in the image below. Which of the following would be the most likely finding on light microscopy in this patient?

Question

A 43-year-old man comes to the office due to shortness of breath and fatigue.  Over the last 2 weeks, his fatigue has been so profound that he has "little energy, even to get out of bed."  The patient has no chills but has experienced recent weight gain and ankle swelling.  He has no prior medical conditions and takes no medications.  Blood pressure is 168/94 mm Hg, and pulse is 95/min and regular.  The patient has bilateral lower extremity pitting edema limited to the ankles.  Urinalysis reveals 2+ protein, white blood cell count of 5-7/hpf, and red blood cell count of 75-100/hpf.  He undergoes a kidney biopsy; immunofluorescent microscopy findings are shown in the image below.  Which of the following would be the most likely finding on light microscopy in this patient?

Quizplus · Accepted Answer

11ec160b_3795_d3f6_9249_bfc19285df12_MD0001_00 This patient has hypertension, hematuria (with mild pyuria), and moderate proteinuria, suggesting a diagnosis of nephritic syndrome. Immunofluorescence microscopy further demonstrates linear deposits of immunoglobulin (typically IgG) and complement along the glomerular basement membrane (GBM), a finding characteristic of anti-GBM disease (Goodpasture disease). Anti-GBM antibodies target collagen type IV, a component of the GBM, leading to subsequent complement deposition. This results in a form of rapidly progressive (crescentic) glomerulonephritis (RPGN). RPGN is a syndrome of severe renal injury that results in abrupt-onset renal injury and decreased glomerular filtration (causing weight gain and edema, as seen in this patient). It can occur due to multiple diseases (eg, granulomatosis with polyangiitis, microscopic polyangiitis). The presence of glomerular crescents-composed of proliferating parietal cells, lymphocytes, macrophages, and fibrin-on light microscopy is diagnostic. Anti-GBM antibodies may cross-react with collagen type IV in the pulmonary alveolar basement membrane and cause pulmonary hemorrhage, which presents as hemoptysis. The combination of renal failure and pulmonary hemorrhage in patients with anti-GBM antibodies is known as Goodpasture syndrome. (Choice A) Renal amyloidosis causes a nephrotic syndrome (ie, heavy proteinuria, hypoalbuminemia, hyperlipidemia, edema); significant hematuria is unexpected. Immunofluorescence microscopy is nonspecific and may show diffuse mesangial staining (rather than distinct, linear immune deposits on the GBM). On Congo red staining, amyloid deposits appear red-pink under light microscopy and have an apple-green birefringence under polarized light. (Choice C) In membranous nephropathy, which causes a nephrotic syndrome, immunofluorescence demonstrates granular deposits of IgG and C3 along the GBM. Uniform, diffuse capillary wall thickening is seen on light microscopy. (Choice D) Nodular glomerulosclerosis (Kimmelstiel-Wilson lesion) and mesangial expansion are seen on light microscopy in diabetic nephropathy, which presents as a nephrotic syndrome. There are no immune deposits on immunofluorescence. (Choice E) Normal glomeruli are found on light microscopy in minimal change disease, a condition that primarily affects children and presents as a nephrotic syndrome. There are no immune deposits on immunofluorescence. Educational objective: Anti-glomerular basement membrane (GBM) antibodies react with collagen type IV, causing rapidly progressive glomerulonephritis with glomerular crescent formation on light microscopy. Immunofluorescence demonstrating linear deposits of IgG and C3 along the GBM is characteristic.

A 43-Year-Old Man Comes to the Office Due to Shortness