A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 54-year-old woman with a long-standing history of hepatitis C infection presents with new-onset hypertension and hematuria. She reports no recent travels or changes in medication. Physical examination reveals mild peripheral edema. Laboratory findings show serum creatinine of 1.6 mg/dL, C3 complement level of 65 mg/dL (normal: 90-180 mg/dL), and a positive test for cryoglobulins. Urinalysis reveals red blood cell casts. Which of the following conditions is most likely responsible for her renal findings?
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A
Membranoproliferative glomerulonephritisCorrect. HCV with low C3, cryoglobulins, and nephritic features classically produces membranoproliferative glomerulonephritis with subendothelial immune complexes.
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B
IgA nephropathyIncorrect. IgA nephropathy presents with synpharyngitic hematuria and normal complement levels, not low C3 with cryoglobulinemia.
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C
Focal segmental glomerulosclerosisIncorrect. FSGS causes nephrotic-range proteinuria without low complement or cryoglobulin association.
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D
Acute interstitial nephritisIncorrect. Acute interstitial nephritis follows drug exposure with eosinophils and WBC casts, not RBC casts and low C3.
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E
Membranous nephropathyIncorrect. Membranous nephropathy is nephrotic with normal complement; it is not driven by cryoglobulin-related complement consumption.
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Answer: A. This patient's renal findings, including low complement levels and positive cryoglobulins, are indicative of membranoproliferative glomerulonephritis (MPGN), often associated with hepatitis C. IgA nephropathy typically presents with normal complement levels, and membranous nephropathy is not associated with low complement levels.