An adolescent with recurrent muscle cramps and hypokalemic metabolic alkalosis has low urinary calcium excretion. Genetic testing confirms loss-of-function mutation in the thiazide-sensitive Na-Cl cotransporter. The diagnosis is:

• A Bartter syndrome type 1
• B Liddle syndrome
• C Gitelman syndrome ✓
• D Pseudohypoaldosteronism type 1

Explanation

Gitelman syndrome results from mutation of the NCCT (SLC12A3) in the distal convoluted tubule, producing a phenotype mimicking chronic thiazide use: hypokalemic alkalosis, hypomagnesemia, and characteristically low urinary calcium. Bartter variants involve the thick ascending limb (NKCC2, ROMK, CLCNKB), impair the concentrating mechanism, and produce hypercalciuria. Liddle syndrome causes hypertension with sodium retention, the opposite salt-wasting picture.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.