Endocrine Abstracts

History: The patient is a 30 year old man who was admitted by ambulance following a witnessed collapse. He had arrived from out of state to visit family and they had spent most of the day house hunting and afterwards, gone out for drinks. It was here that he collapsed and became unconscious, with immediate bystander CPR given, until arrival of the crew who carried out a 25 minute resuscitation with six shocks given. He was intubated and transported to the hospital into the intensive care unit. His medical history was of mild asthma for which he took salbutamol inhalers infrequently, with no acute exacerbations requiring hospital admission. No other medications of note. His blood pressure on arrival was 142/84mmHg having received metaraminol for hypotension and heart rate 136b/m.

Investigations and Results: Electrogardiogram was normal sinus rhythm. Initial mixed acidosis on venous blood gas with PH 7.23, anion gap 25.2, bicarbonate 19.9, PCO2 7.28 likely due to the arrest and resuscitation. This however reverted to a persistent metabolic alkalosis by the second day of admission: PH 7.52, bicarbonate 29.6, anion gap 6.5. Serum potassium was 2.1 mmol/l (3.5 -5.3), magnesium 0.88 mmol/l (0.7 - 1.07), chloride 92 mmol/l, sodium 138 mmol/l, calcium 2.14 mmol/l (2.20 - 2.6). Urine biochemistry on day 2 showed high urine potassium of 106 mmol/l in the presence of hypokalaemia, urine sodium 46 mmol/l, with normal urine calcium and magnesium. Serum renin and aldosterone were elevated. Our working diagnosis: salt-wasting nephropathy (Gitelman’s vs Bartter’s syndrome) to exclude long QT syndromes.

Treatment: He required vasopressor support in ITU, nutrition management and electrolyte replacement therapy often needing multiple doses of intravenous potassium, magnesium and phosphate to maintain normal levels. He underwent cardiology work-up including coronary angiogram, cardiac MRI and Ajmaline testing which were all negative. However a decision was made to insert an implantable defibrillator to minimise future recurrence of cardiac arrest. A genetic analysis revealed that he is heterozygous for the SLC12A3 pathogenic variant consistent with Gitelman’s syndrome.

Conclusion and points for discussion: As this is a rare presentation of Gitelman’s syndrome, it is worth highlighting this as a frontline consideration in severe hypokalaemia in a fit young adult especially when presenting acutely like this. Historically, Gitelman’s syndrome is considered a mild chronic disease, with many patients remaining asymptomatic. Many patients may not exhibit the classic features initially, but a high index of suspicion should be maintained at all times.