A 45-year-old man presents with acute onset hematuria, dysmorphic red blood cells, and RBC casts in urine. Serum creatinine has risen from 1.0 mg/dL to 4.2 mg/dL over 10 days. Kidney biopsy shows the lesion marked **A** — a proliferation of parietal epithelial cells and macrophages with fibrin filling Bowman's space, compressing the glomerular tuft. This histopathologic finding is the hallmark of which clinical syndrome?