Rare diseases · Sign or symptom
Dilated third ventricle
HP:0007082
What it means
An increase in size of the third ventricle.
The third ventricle is midline between the two lateral ventricles, and it communicates between them and the fourth ventricle.
Rare diseases that can present with this7
Sometimes5–29%
5- Autosomal dominant cerebellar ataxia-deafness-narcolepsy syndrome
- Basel-Vanagaite-Smirin-Yosef syndrome
- Global developmental delay-alopecia-macrocephaly-facial dysmorphism-structural brain anomalies syndrome
- Joubert syndrome with Jeune asphyxiating thoracic dystrophy
- X-linked parkinsonism-spasticity syndrome
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
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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.