rss
BMJ Case Reports 2015; doi:10.1136/bcr-2013-009111
  • CASE REPORT

Reset osmostat: a rare cause of hyponatraemia

  1. Gabriela Mimoso2
  1. 1Hospital Pediátrico, Centro Hospitalar Universitário de Coimbra, Portugal
  2. 2Maternidade Bissaya Barreto do Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal
  1. Correspondence to Dr Beatriz Vale, beatriz_vale{at}hotmail.com
  • Accepted 3 June 2015
  • Published 29 June 2015

Summary

Neonatal hyponatraemia is common, and related to significant morbidity and mortality. We report a case of a preterm newborn (gestational age of 36 weeks) with hyponatraemia, and with a prenatal diagnosis of cleft lip and palate, with a normal fetal karyotype. On the seventh day of life, a biochemical evaluation for jaundice and mild signs of dehydration showed hyponatraemia of 124 mmol/L. Investigation showed normal adrenal and thyroid functions, plasma hyposmolality (258 mOsm/kg); high urinary sodium (73 mmol/L) and high urinary osmolality (165 mOsm/kg). Despite oral sodium supplementation and fludrocortisone treatment, sodium levels remained between 124 and 130 mmol/L. Cranial ultrasound, brain MRI and renal ultrasound were normal. The diagnosis of hyponatraemia was unpredicted and the investigation was suggestive of reset osmostat, a subtype of the syndrome of inappropriate secretion of antidiuretic hormone, characterised by a subnormal threshold for antidiuretic hormone secretion.

Register for free content

The full text of all Editor's Choice articles and summaries of every article are free without registration

The full text of Images in ... articles are free to registered users

Only fellows can access the full text of case reports (apart from Editor's Choice) - become a fellow today, or encourage your institution to, so that together we can grow and develop this resource

Don't forget to sign up for content alerts so you keep up to date with all the case reports as they are published, and let us know what you think by commenting on the Editor's blog

Navigate This Article