A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 30-year-old man with a family history of genetic kidney disorders presents with recurrent episodes of hematuria and flank pain. He denies any urinary frequency or fever. Physical examination is unremarkable. Laboratory tests show normal serum electrolytes and renal function. A renal ultrasound shows multiple small cysts in the medulla with a 'paintbrush' appearance. Which genetic component is most likely linked to his condition?
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A
Mutation in GDNF geneCorrect. Medullary sponge kidney has been linked to mutations involving the GDNF/RET signaling pathway that regulates ureteric bud development.
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B
Mutation in COL4A5 geneIncorrect. COL4A5 mutations cause Alport syndrome (X-linked), presenting with glomerular hematuria and deafness, not medullary cysts.
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C
Mutation in TSC1 geneIncorrect. TSC1 mutations cause tuberous sclerosis with cortical tubers and angiomyolipomas, not the MSK paintbrush pattern.
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D
Mutation in MUC1 geneIncorrect. MUC1 mutations cause autosomal dominant tubulointerstitial kidney disease (MCKD type 1), not medullary sponge kidney.
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E
Mutation in PKD1 geneIncorrect. PKD1 mutations cause ADPKD with large cortical/medullary cysts, not the medullary paintbrush appearance of MSK.
↑ Tap an answer to reveal the reasoning
Answer: A. The clinical and imaging findings are indicative of medullary sponge kidney, which is potentially linked to a mutation in the GDNF gene. PKD1 mutations are associated with polycystic kidney disease, which presents differently, ruling out choice A.