HNF1B variant without hyperglycaemia as a cause of isolated profound hypomagnesaemia

Shobitha Vollmer, Per Katzman, Magnus Londahl

Research output: Contribution to journalArticlepeer-review


A young man presented unconscious with severe hyponatraemia, hypokalaemia, hypomagnesaemia and metabolic alkalosis. After 4 months of treatment in hospital, the hypomagnesaemia persisted. The patient had no signs of diabetes mellitus, and radiology showed no abnormalities of the kidneys, pancreas or genitourinary tract. A parenteral magnesium load demonstrated renal wasting with increased fractional urinary excretion of magnesium. Genetic tests for Gitelman as well as Bartter syndromes were negative. However, a wider genetic panel revealed that the patient was heterozygous for a deletion on chromosome band 17q12, encompassing the whole HNF1B gene.This case highlights the importance of considering pathogenic HNF1B variants in isolated profound hypomagnesaemia caused by renal wasting. Pathogenic HNF1B variants may partly mimic hypomagnesaemia found in Gitelman and Bartter syndromes and may be present without other features linked to HNF1B variants, including diabetes mellitus.

Original languageEnglish
JournalBMJ Case Reports
Issue number2
Publication statusPublished - 2023 Feb 9

Subject classification (UKÄ)

  • Medical Genetics
  • Endocrinology and Diabetes

Free keywords

  • Diabetes
  • Fluid electrolyte and acid-base disturbances
  • Genetic screening / counselling
  • Genetics


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