A 42-year-old man presents with acute kidney injury (creatinine 4.2 mg/dL, baseline 0.9 mg/dL over 10 days), hematuria with dysmorphic red blood cells and RBC casts, and hypertension. Renal biopsy shows the pathologic findings illustrated in the diagram. The structure marked **A** is identified on light microscopy in >50% of glomeruli. Which of the following clinical features is MOST consistent with the pathologic finding at **A** and its underlying pathogenesis?