Renal failure
philomena - 07-09-11 14:59

A 62-year-old man comes to the physician because of a 3-month history of progressive fatigue and joint pain, a
2-month history of sinus congestion, a 3-week history of cough, and a 1-week history of blood-tinged sputum.
He has not had fever, nausea, vomiting, or diarrhea. He has hypercholesterolemia, stable angina pectoris, and
hypertension. Medications include atorvastatin, labetalol, isosorbide, and aspirin. Over the past 3 weeks, he has
been taking over-the-counter ibuprofen as needed for the joint pain. His pulse is 84/min, respirations are
12/min, and blood pressure is 132/76 mm Hg. Examination shows clear nasal discharge with no nasal or oral
lesions. The joints are diffusely tender with no warmth or erythema; range of motion is full. Laboratory studies
show:
Hematocrit 36%
Mean corpuscular volume 83 μm3
Leukocyte count 14,000/mm3
Segmented neutrophils 74%
Eosinophils 1%
Lymphocytes 14%
Monocytes 11%
Platelet count 275,000/mm

Serum
Urea nitrogen 28 mg/dL
Creatinine 3.2 mg/dL
Antinuclear antibodies 1:256
Rheumatoid factor negative
Antineutrophil cytoplasmic antibodies positive

Urine
Blood 3+
Protein 3+
RBC 15–17/hpf
WBC 1–2/hpf
RBC casts rare

Which of the following is the most likely underlying mechanism of this patient's renal failure?