A 38-year-old woman comes to the physician because of a 2-week history of blood in the urine and fatigue. She coughed up a small amount of blood one week ago that she attributed to a recent sore throat she had. Laboratory studies are positive for anti-proteinase 3 antibodies. A renal biopsy is shown. Which of the following is most likely to be seen in this patient?
Decreased complement protein C3
Decreased complement protein C4
Deficiency of C1q
Foot drop
Linear immunofluorescence
