A 5-year-old girl is brought to the clinic due to 2 days of dark red urine. The patient was treated for facial impetigo 1 month ago. Blood pressure is 140/90 mm Hg. Urinalysis reveals hematuria, mild proteinuria, and occasional red blood cell casts. Which of the following changes would most likely be present on this patient's renal biopsy?

Question

A 5-year-old girl is brought to the clinic due to 2 days of dark red urine.  The patient was treated for facial impetigo 1 month ago.  Blood pressure is 140/90 mm Hg.  Urinalysis reveals hematuria, mild proteinuria, and occasional red blood cell casts.  Which of the following changes would most likely be present on this patient's renal biopsy?

Quizplus · Accepted Answer

11ec160b_3a42_cc18_9249_430c16ddeb6b_MD0001_00 This patient has nephritic syndrome, characterized by hypertension, mild proteinuria, and hematuria with red blood cell casts in the urine sediment. In association with a recent skin infection, this presentation suggests poststreptococcal glomerulonephritis (PSGN), the most common cause of nephritic syndrome in children. PSGN is an immune complex-mediated disease that occurs 2-4 weeks after exposure to group A beta-hemolytic Streptococcus (eg, pharyngitis, skin infection). Antigens expressed on nephritogenic streptococcal species combine with antibodies to form immune complexes, which are later deposited on the glomerular basement membrane (GBM). On light microscopy, all glomeruli are enlarged and hypercellular due to leukocyte infiltration and proliferation of endothelial and mesangial cells. On electron microscopy, electron-dense deposits ("humps") on the epithelial side of the GBM are seen. Immunofluorescence reveals coarse, granular deposits of IgG and C3 that have a characteristic "lumpy-bumpy" appearance. (Choice A) Uniform, diffuse thickening of glomerular capillary walls on light microscopy is characteristic of membranous glomerulopathy, one of the most common causes of nephrotic syndrome in adults. Manifestations of nephrotic syndrome include generalized edema, marked proteinuria (>3.5 g/day), hypoalbuminemia, hyperlipidemia, and lipiduria. (Choices C and E) In contrast to PSGN, which demonstrates granular deposits of IgG and C3 along the GBM, linear IgG and C3 deposits on immunofluorescence microscopy are characteristic of Goodpasture syndrome (anti-GBM disease). This commonly presents with rapidly progressive (crescentic) glomerulonephritis. Damage to the GBM results in leakage of plasma proteins and heavy fibrin deposition in the glomerulus, resulting in parietal cell proliferation and crescent formation. This disease is uncommon in children, and renal involvement is often accompanied by pulmonary symptoms (eg, hemoptysis). (Choice D) GBM splitting is seen in membranoproliferative glomerulonephritis (MPGN) and Alport syndrome. Alport syndrome causes nephritic syndrome but is most commonly X-linked and therefore more common in males; it is not associated with recent streptococcal infections. MPGN causes nephrotic syndrome. Educational objective: Poststreptococcal glomerulonephritis is an immune complex-deposition disease that occurs 2-4 weeks after exposure to group A beta-hemolytic Streptococcus species (eg, pharyngitis, skin infection). Light microscopy shows enlarged, hypercellular glomeruli. Immunofluorescence demonstrates a "lumpy-bumpy" granular deposits of IgG and C3 on the glomerular basement membrane, and subepithelial, electron-dense deposits are seen on electron microscopy.

A 5-Year-Old Girl Is Brought to the Clinic Due to 2