Endocrine Abstracts

Background: Infants presenting with life threatening hyponatraemia and hyperkalaemia present a diagnostic conundrum that can reflect abnormally low aldosterone production (e.g. congenital adrenal hyperplasia (CAH), renal resistance to aldosterone associated with infected urinary tract malformations or single gene disorders also associated with failure of the kidney to respond to aldosterone (pseudohypoaldosteronism). Although incidence figures for individual conditions exist, no overall data exists for presentation of this characteristic laboratory pattern and underlying cause.

Method: Population-based surveillance study July 2021 to June 2023. Cases were identified by paediatricians using the monthly electronic Welsh Paediatric Surveillance Unit (WPSU) reporting system. Hospital biochemists and tertiary specialists were recruited to optimise ascertainment. Inclusion criteria were term infants <12 months with sodium <130 mmol/L (<2.5 S.D.) AND Potassium >5.5 mmol/L (>2.5 S.D.).

Results: 13 notifications were reported with two additional cases identified by receiving subspecialists. In total 10 infants over two years met inclusion criteria, resulting in an incidence of 1.7 cases of low sodium and high potassium per 10 000 infants per year. Eventual diagnoses were: 3 CAH, 4 transient pseudohypoaldosteronism (3 with underlying urinary infection and urinary tract malformation), one associated with RSV bronchiolitis, one associated with maternal hyponatraemia, one uncertain. Details of eight cases were available by abstract submission deadline. All were white ethnicity infants with birth weights >3 kg. 50% were male. Infants presented at median 14 days old (1 hour to 3 months). 4/7 (57%) were shocked or with >10% weight loss. All received 0.9% normal saline fluid boluses with 1/7 receiving insulin for hyperkalemia. Serum sodium and potassium corrected by median one day after admission (range 0–3 and 0–2 days respectively). Patients were discharged after median 6 days (range 3–17). One infant represented after one week with a seizure with normal neuro-imaging and examination. No other sequelae were reported at one month follow up.

Conclusion: This first ever study of infants presenting with severe hyponatraemia and hyperkalaemia across a whole population confirms that this biochemical picture is rare. Most have either CAH or renal aetiology. Normalisation of biochemistry derangement was rapid, and short-term outcome was favourable.