Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 28-year-old man is evaluated for a 2-month history of progressive lower-extremity edema, weight loss, and fatigue. Medical history is significant for recreational use of inhaled cocaine; he denies injection drug use. He has no other known medical issues and takes no medications.
On physical examination, temperature is 37.2 °C (99.0 °F), blood pressure is 130/90 mm Hg, pulse rate is 90/min, and respiration rate is 20/min. BMI is 28. Temporal wasting is present. The lungs are clear. Cardiac examination is normal, and no pericardial rub is detected. There is no hepatosplenomegaly or evidence of ascites on abdominal examination. The lower extremities show edema to the knees bilaterally. Skin and joint examinations are normal. Mild asterixis is noted.
Laboratory studies:
| Albumin | 2.5 g/dL (25 g/L) |
| Liver chemistry studies | Normal |
| Blood urea nitrogen | 98 mg/dL (35 mmol/L) |
| Creatinine | 6.8 mg/dL (601.1 µmol/L) |
| Urinalysis | 1+ blood; 3+ protein; 5 erythrocytes/hpf; 0-2 leukocytes/hpf |
| Urine protein-creatinine ratio | 3700 mg/g |
Kidney ultrasound shows mildly enlarged and echogenic kidneys without obstruction.
Kidney biopsy results are indicative of the collapsing variant of focal segmental glomerulosclerosis (FSGS).
Which of the following tests is most likely to establish the cause of this patient’s FSGS?
A. Hepatitis B and C serologies
B. HIV antibody test
C. Serum and urine electrophoresis
D. Treponemal antibody test
MKSAP Answer and Critique
The correct answer is B. HIV antibody test.
The most appropriate test to perform is an HIV antibody test in this patient with focal segmental glomerulosclerosis (FSGS). FSGS is the cause of idiopathic nephrotic syndrome in 25% of cases. FSGS may also be secondary to another process, including hyperfiltration injury to the glomerulus as may occur in chronic hypertension, diabetes mellitus, and conditions in which kidney mass is reduced (progressive kidney disease, obesity, sickle cell disease, reflux nephropathy, or after nephrectomy). Direct injury to podocytes may also cause FSGS as seen with certain drugs (pamidronate, interferon) and infections, including HIV. This patient’s kidney biopsy results are indicative of the collapsing variant of FSGS, which is classic for HIV-associated glomerulopathy. Therefore, evaluation for HIV infection as a cause of this patient’s FSGS is the most appropriate next diagnostic step. In the early stages of HIV-associated glomerulopathy, antiretroviral therapy and angiotensin system blockers may halt disease progression, thus an early diagnosis is important.
Hepatitis B is typically associated with membranous glomerulopathy, and hepatitis C with cryoglobulinemic glomerulonephritis. Serum and urine electrophoresis can be used to test for monoclonal gammopathies. The treponemal antibody test is used to test for syphilis, which is typically associated with membranous nephropathy. None of these disorders is associated with the collapsing glomerulopathy seen on this patient’s kidney biopsy.
Key Point
- HIV infection is typically associated with the collapsing form of focal segmental glomerulosclerosis; in the early stages, antiretroviral therapy and angiotensin system blockers may halt disease progression.
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