Problems in diagnosing atypical Gitelman's syndrome presenting with normomagnesaemia

Area of Science:

• Nephrology
• Genetics
• Internal Medicine

Background:

• Gitelman syndrome is a variant of Bartter syndrome, presenting with hypokalemia, metabolic alkalosis, hypomagnesemia, and hypocalciuria.
• Overlapping biochemical profiles between Gitelman and Bartter syndromes complicate diagnosis.
• Accurate diagnosis is crucial for appropriate management and understanding of these renal tubular disorders.

Purpose of the Study:

• To investigate the clinical, biochemical, and genetic characteristics of five Japanese patients with chronic hypokalemia.
• To differentiate Gitelman syndrome from Bartter syndrome using advanced diagnostic techniques.
• To assess the utility of renal clearance tests and genetic analysis in diagnosing Gitelman syndrome.

Main Methods:

• Collected serum and urinary electrolytes, plasma renin activity, and aldosterone concentrations.
• Performed renal clearance tests, including furosemide and thiazide administration, to assess chloride reabsorption.
• Conducted mutational analysis of the thiazide-sensitive Na-Cl co-transporter gene (SLC12A3).

Main Results:

• Patients exhibited variable symptoms, from muscle weakness to paralysis, all with hypokalemia and hypocalciuria.
• Two patients presented with normomagnesemia, an atypical finding for Gitelman syndrome.
• Renal clearance tests and identification of six SLC12A3 gene mutations, including two novel ones, confirmed Gitelman syndrome diagnoses.

Conclusions:

• Normomagnesemia can occur in Gitelman syndrome, challenging traditional diagnostic criteria.
• Renal clearance tests and genetic mutation analysis are essential for precise diagnosis of Gitelman syndrome.
• This study underscores the importance of molecular diagnostics in characterizing rare renal tubular disorders.