A 41-year-old man comes to the physician for a 3-week history of occasional dark urine. He also reports having coughed up sputum with blood about a week ago. Past medical history is unremarkable. Head and neck examination shows no abnormalities. He takes no medications. A renal biopsy from a similar patient is shown. Which of the following is most likely to be seen in this patient?
Antibodies against basement membranes
c-ANCA
Collagen IV gene mutation
Focal segmental glomerulosclerosis
Necrosis of papillae
