A Rare Paediatric Case of AVPR2-Related Nephrogenic Syndrome of Inappropriate Antidiuresis in Penang
https://doi.org/10.15605/jafes.041.S1
- Author:
Wei Lian Lean
1
;
Raja Aimee Binti Raja Abdullah
1
;
Gaik Siew Ch’ng
2
;
Voon Lee Lim
3
Author Information
1. Paediatric Endocrinology Unit, Department of Paediatric, Hospital Pulau Pinang
2. Genetic Unit, Hospital Pulau Pinang
3. General Paediatric, Department of Paediatric, Hospital Pulau Pinang
- Publication Type:Journal Article
- MeSH:
Child;
Nephrogenic Syndrome of Inappropriate Antidiuresis
- From:
Journal of the ASEAN Federation of Endocrine Societies
2026;41(S1):141-
- CountryPhilippines
- Language:English
-
Abstract:
Introduction:Nephrogenic syndrome of inappropriate antidiuresis
(NSIAD) is an uncommon X-linked genetic condition
marked by euvolemic hyponatremia, which arises from
a gain-of-function mutation in the arginine vasopressin
receptor type 2 (AVPR2) gene. In contrast to the classic
syndrome of inappropriate antidiuretic hormone
secretion (SIADH), NSIAD is characterized by urine
that is inappropriately concentrated even when arginine
vasopressin (AVP) levels are low or undetectable. Failure
to recognize NSIAD may result in recurrent hyponatremia
and neurological morbidity.
Case:A 2-year-old male was referred to us after recurrent
vomiting and subsequently developed generalized tonicclonic seizures due to hyponatremia (with a sodium level
of 115 mmol/L). He needed sodium replacement through
an intravenous drip of 3% saline and was stabilized with
oral sodium chloride 20%. Urine osmolality was elevated,
serum osmolality remained normal, and copeptin levels
were low. He was discharged after a 10-day hospital stay.
During follow-up, hyponatremia recurred despite his
typical fluid intake of 1,200 mL/day. He was instructed to
limit his fluid intake to 600–700 mL, which successfully
normalized his serum sodium levels. Serum levels of
adrenocorticotropic hormone, the aldosterone-to-renin
ratio, thyroid function tests, and serum cortisol were all
within normal ranges. Plasma AVP was unusually low (4.0
pmol/L). Whole exome sequencing (WES) confirmed a likely
pathogenic hemizygous variant in AVPR2 gene located on
chromosome Xq28, which was inherited from his mother.
He is the only child, born from a non-consanguineous
marriage, with no other significant family medical history.
Conclusion:Nephrogenic syndrome of inappropriate antidiuresis
(NSIAD), is an uncommon, yet clinically significant
condition. This case highlights the importance of considering a broad range of differential diagnoses when a patient presents with hyponatremic seizure. Furthermore,
obtaining a detailed family history is essential to identify
potential hereditary factors that could contribute to the
condition and for genetic counseling.
- Full text:2026081013363410412EP_P012.pdf
