Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 25-year-old man is evaluated for dark-colored urine for 2 days, swelling of the face and hands for 1 day, and severe headaches this morning. He reports having an upper respiratory tract infection 1 week ago with fever, sore throat, and swollen glands, but had otherwise felt well. Medical history is otherwise unremarkable, and he takes no medications.
On physical examination, temperature is 37.2 °C (99.0 °F), blood pressure is 180/90 mm Hg, pulse rate is 88/min, and respiration rate is 14/min. Cardiopulmonary and abdominal examinations are normal. No skin rash or arthritis is present. There is bilateral lower extremity edema to the mid shins.
Laboratory studies:
| Albumin | 3.3 g/dL (33 g/L) |
| C3 | Low |
| C4 | Normal |
| Creatinine | 1.4 mg/dL (124 µmol/L) |
| Antistreptolysin O antibodies | Elevated |
| Urinalysis | 3+ blood; 2+ protein; too numerous to count erythrocytes/hpf; 10-15 leukocytes/hpf; numerous erythrocyte casts |
| Urine protein-creatinine ratio | 1900 mg/g |
| Rapid streptococcal antigen test | Positive |
Which of the following is the most likely diagnosis?
A. IgA nephropathy
B. Infection-related glomerulonephritis
C. Lupus nephritis
D. Small-vessel vasculitis
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