A 2nd-year internal medicine resident is preparing a presentation on inherited and acquired renal tubular disorders. Match each of the following tubulopathies with its primary pathophysiological defect or defining molecular characteristic.
- Fanconi syndromeGeneralized proximal tubule transport defect causing aminoaciduria and glycosuria
- Bartter syndromeDefect in the Na+-K+-2Cl- cotransporter in the thick ascending limb
- Gitelman syndromeDefect in the Na+-Cl- cotransporter in the distal convoluted tubule
- Liddle syndromeGain-of-function mutation in the epithelial sodium channel (ENaC)
- Syndrome of apparent mineralocorticoid excessDeficiency of 11-beta-hydroxysteroid dehydrogenase type 2 enzyme
Answer
Fanconi syndrome matches with the generalized proximal tubule defect; Bartter syndrome matches with the Na+-K+-2Cl- cotransporter defect; Gitelman syndrome matches with the Na+-Cl- cotransporter defect; Liddle syndrome matches with the ENaC gain-of-function mutation; Syndrome of apparent mineralocorticoid excess matches with the 11-beta-hydroxysteroid dehydrogenase type 2 enzyme deficiency.
Renal tubulopathies are characterized by specific transporter or enzymatic defects along the nephron. Fanconi syndrome causes global proximal tubular dysfunction. Bartter syndrome affects the NKCC2 transporter in the thick ascending limb. Gitelman syndrome involves the NCC transporter in the distal convoluted tubule. Liddle syndrome is driven by an overactive ENaC in the collecting duct. Finally, the syndrome of apparent mineralocorticoid excess results from a deficiency in 11-beta-hydroxysteroid dehydrogenase type 2, which normally prevents circulating cortisol from acting on mineralocorticoid receptors in the kidney.
Step-by-Step Solution
Key Concept
Understanding the specific anatomical and molecular defects of renal tubulopathies is essential for predicting their clinical and laboratory manifestations.