Rare diseases · Sign or symptom
Hallucinations
Hallucination
HP:0000738
What it means
Perceptions in a conscious and awake state that, in the absence of external stimuli, have qualities of real perception. These perceptions are vivid, substantial, and located in external objective space.
Rare diseases that can present with this50
Very common80–99%
6Common30–79%
11- Caribbean parkinsonism
- Childhood-onset schizophrenia
- Citrullinemia type II
- Fatal familial insomnia
- Frontotemporal dementia with motor neuron disease
- Huntington disease
- Metachromatic leukodystrophy, adult form
- NMDA receptor encephalitis
- Pellagra
- Subacute sclerosing leukoencephalitis
- Young-onset Parkinson disease
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: Sensory hallucination
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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.