Introduction:

Hypokalaemia is a common clinical problem. A potential but commonly overlooked cause of hypokalaemia is Gitelman syndrome.

Material and methods:

A 26-year-old man was admitted to the hospital due to syncope with general and muscular weakness and muscle cramps. The patient's history revealed previous recurrent syncope events associated to hypokalaemia with the lowest serum potassium value being 2.6 mmol/l. At admission, blood pressure was normal and no changes were found at physical examination. Laboratory tests showed mild hypokalaemia (3.0 mmol/l), hypomagnesaemia (1.36 mg/dl), hypocalciuria (< 40 mg/24 h), and metabolic alkalosis (HCO3− 29.7 mmol/l, BE 5.3 mmol/l).

Results:

Further laboratory tests (FeK, TTKG) confirmed inappropriate kaliuresis. Conn's disease was excluded by hormonal and imaging assessments. Genetic testing was performed and two novel heterozygous mutations: c.35_36insA and c.1095+5G>A were found in transcript NM_000339.2 in SLC12A3 gene.

Conclusion:

The patient was diagnosed with Gitelman syndrome and was treated with supplements of potassium and magnesium.