Tiopronin Cystinuria Stepwise — ESENeph MCQ

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HardRenal Stone DiseaseTiopronin Cystinuria StepwiseESENeph

A young man has low-molecular-weight proteinuria, hypercalciuria, nephrocalcinosis and progressive CKD. Which molecular defect most commonly explains this X-linked phenotype?

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Correct answer: D — A CLCN5 defect impairing proximal-tubule endosomal processing

The best answer is “A CLCN5 defect impairing proximal-tubule endosomal processing”. ClC-5 dysfunction disrupts proximal tubular receptor-mediated endocytosis, producing low-molecular-weight proteinuria and hypercalciuria; OCRL variants cause Dent disease type 2. “An AQP2 defect impairing collecting-duct water reabsorption” is less appropriate because that causes nephrogenic diabetes insipidus rather than Dent disease “An ENaC gain-of-function mutation” is less appropriate because that produces Liddle syndrome with hypertension and hypokalaemia “An NKCC2 defect in the thick ascending limb” is less appropriate because that produces a Bartter phenotype “An NPHS2 podocyte defect” is less appropriate because that causes steroid-resistant nephrotic syndrome

Reference: GeneReviews: Dent disease: https://www.ncbi.nlm.nih.gov/books/NBK99494/