GITELMANS SYNDROME - A DIFFERENTIAL-DIAGN OSIS OF BARTTERS-SYNDROME

Background: Hypokalemia due to renal potassium wasting in the absence of hypertension, moderate metabolic alkalosis, hyperreninism and hyper aldosteronism suggest the presence of Bartter's syndrome. The underlyi ng cause is an inherited de feet of sodium chloride reabsorption in th e thick ascending limb of Henle. A differential diagnosis of Bartter's syndrome is Gitelman's syndrome, another hypokalemia-hypomagnesemia s yndrome, which is thought to be caused by a transport defect in the di stal tube. Patients and Methods: We report 3 patients presenting with signs primarily suggestive of Bartter's syndrome, who turned out to ha ve Gitelman's syndrome after determing the excretion of calcium in the urine. Results: Two women, 36- and 55-year old, suffered from paresth esias in the hands and feet and from tetanic convulsions. The brother of the 36-year old woman presented in our hospital because of an accid entally discovered hypokalemia without any clinical symptoms. In all p atients the outstanding biochemical features were hypokalemia, hypomag nesemia and moderate metabolic alcalosis. The renin and aldosteron val ues were inappropriately high. The most characteristic finding in the urine, besides the presence of hyperkaliuria was the diminution of cal cium excretion, despite normocalcemia. Conclusion: The association bet ween sodium and calcium reabsorption in the loop of HenIe predicts hyp ercalciuria in patients with a defect in salt reabsorption in this seg ment, as in Bartter's syndrome. In Gitelman's syndrome the laboratory features resemble the findings in Bartter's syndrome, except for the p resence of hypocalciuria. Since hypocalciuria follows also the adminis tration of thiazide diuretics, which act in the early part of distal t ube, a transport defect in this part of the tube is thought to be resp onsible for the electrolyte disturbances in Gitelman's syndrome. The m easurement of the urinary calcium excretion in patients with an unclea r hypokalemia-hypomagnesemia-syndrome allows easily the differentiatio n between Bartter's and Gitelman's syndrome.