Rare diseases · Sign or symptom
Hyponatremia
Low blood sodium levels
HP:0002902
What it means
The concentration of sodium in the blood circulation is below the lower limit of normal.
Rare diseases that can present with this58
Very common80–99%
10- 46,XY difference of sex development-adrenal insufficiency due to CYP11A1 deficiency
- Congenital isolated ACTH deficiency
- Deficiency in anterior pituitary function-variable immunodeficiency syndrome
- Early-onset familial hypoaldosteronism
- Familial hypoaldosteronism
- Generalized pseudohypoaldosteronism type 1
- Hearing loss-familial salivary gland insensitivity to aldosterone syndrome
- Inherited isolated adrenal insufficiency due to partial CYP11A1 deficiency
- Oculocerebrorenal syndrome of Lowe
- Rapid-onset childhood obesity-hypothalamic dysfunction-hypoventilation-autonomic dysregulation syndrome
Common30–79%
18- Acute adrenal insufficiency
- Addison disease
- ALG8-CDG
- Autosomal recessive polycystic kidney disease
- Bartter syndrome type 4
- Cholera
- Classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency
- Colchicine poisoning
- Congenital adrenal hyperplasia due to 3-beta-hydroxysteroid dehydrogenase deficiency
- Congenital lipoid adrenal hyperplasia due to STAR deficency
- Familial glucocorticoid deficiency
- Herpes simplex virus encephalitis
- Late-onset isolated ACTH deficiency
- Necrotizing enterocolitis
- Pituitary apoplexy
- Posttransplant acute limbic encephalitis
- Steroid-responsive encephalopathy associated with autoimmune thyroiditis
- X-linked adrenal hypoplasia congenita
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Decreased sodium(1+) concentration · Decreased sodium(1+) level · Decreased sodium(1+) level in blood · Reduced sodium(1+) concentration · Reduced sodium(1+) level · Reduced sodium(1+) level in blood
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.