A 12-year-old boy is brought to the clinic because of facial puffiness. Examination shows periorbital edema. Urinalysis reveals: A biopsy image representative of this patient's disease process is shown below. Which of the following additional findings is most likely to be present in this patient?

Question

A 12-year-old boy is brought to the clinic because of facial puffiness.  Examination shows periorbital edema.  Urinalysis reveals:  A biopsy image representative of this patient's disease process is shown below.  Which of the following additional findings is most likely to be present in this patient?

Quizplus · Accepted Answer

11ec160b_3a43_8f6b_9249_cfd272f14389_MD0001_00 This pediatric patient with microscopic hematuria, red blood cell casts, mild pyuria, and proteinuria has a nephritic syndrome (glomerulonephritis). The biopsy sample demonstrates enlarged, hypercellular glomeruli consistent with poststreptococcal glomerulonephritis (PSGN), which is the most common cause of nephritic syndrome in children. PSGN is caused by immune complex deposition in the glomerulus following group A beta-hemolytic Streptococcus (eg, Streptococcus pyogenes) infection. Hypercellularity, which involves all lobules of all glomeruli, is the result of leukocyte infiltration and endothelial and mesangial cell proliferation in response to secreted cytokines. Other classic findings include elevated titers of antistreptococcal antibodies (eg, antistreptolysin O, anti-DNase B) and low C3 concentrations (due to consumption). Electron microscopy typically shows electron-dense deposits composed of immune complexes on the epithelial side of the glomerular basement membrane. On immunofluorescent microscopy, there are coarse, granular deposits of IgG and C3 with a characteristic "starry sky" appearance. (Choices A and B) Serum antiglomerular basement membrane antibodies are found in Goodpasture syndrome. Serum antineutrophil cytoplasmic antibodies are associated with certain vasculitides (eg, granulomatosis with polyangiitis, microscopic polyangiitis). These conditions can cause both pulmonary-renal syndrome with hemoptysis and renal failure. However, the typical renal manifestation is rapidly progressive glomerulonephritis, which is characterized by crescent formation on light microscopy. In addition, these conditions are rare in children. (Choice D) Although C3 levels are decreased in almost all patients with PSGN, C4 levels are usually normal as complement activation in PSGN occurs predominantly via the alternative pathway. (Choice E) Eosinophilia can occur in acute interstitial nephritis, which causes renal failure but is typically associated with fever, rash, sterile pyuria, and white blood cell casts; significant hematuria and red blood cell casts are unexpected. Educational objective: Poststreptococcal glomerulonephritis is the most common cause of nephritic syndrome in children. Light microscopy demonstrates enlarged, hypercellular glomeruli. Laboratory findings in poststreptococcal glomerulonephritis include elevated antistreptococcal antibodies (eg, antistreptolysin O, anti-DNase B) and decreased C3 and total complement levels. C4 levels are usually normal.

A 12-Year-Old Boy Is Brought to the Clinic Because of Facial