Rare diseases · Sign or symptom
Encephalopathy
HP:0001298
What it means
Encephalopathy is a term that means brain disease, damage, or malfunction. In general, encephalopathy is manifested by an altered mental state.
This term and its children are general and bundled terms that are kept for convenience. For new annotations, it is recommended that the specific phenotypic abnormalities be noted.
Rare diseases that can present with this64
Very common80–99%
12- 3-methylglutaconic aciduria type 9
- Carnitine-acylcarnitine translocase deficiency
- Cerebellar ataxia-areflexia-pes cavus-optic atrophy-sensorineural hearing loss syndrome
- Classic glucose transporter type 1 deficiency syndrome
- Encephalitis lethargica
- Ethylmalonic encephalopathy
- Gaucher disease type 2
- Gaucher disease type 3
- Isolated complex I deficiency
- Lennox-Gastaut syndrome
- MECP2-related severe neonatal encephalopathy
- Non-specific early-onset epileptic encephalopathy
Common30–79%
17- 3-methylglutaconic aciduria-neonatal cataract-neurologic involvement-congenital neutropenia syndrome
- Acyl-CoA dehydrogenase 9 deficiency
- Aminoacylase 1 deficiency
- Congenital bile acid synthesis defect type 4
- Fatal infantile lactic acidosis with methylmalonic aciduria
- Folinic acid-responsive seizures
- Fumaric aciduria
- Hepatoencephalopathy due to combined oxidative phosphorylation defect type 1
- Homocystinuria without methylmalonic aciduria
- Isolated ATP synthase deficiency
- Kaposi sarcoma
- MEGDEL syndrome
- MELAS
- Mitochondrial DNA-related cardiomyopathy and hearing loss
- Mitochondrial hypertrophic cardiomyopathy with lactic acidosis due to MTO1 deficiency
- Multiple mitochondrial dysfunctions syndrome type 1
- Ornithine transcarbamylase deficiency
Sometimes5–29%
22- 3-hydroxy-3-methylglutaric aciduria
- Acute liver failure
- Adult-onset Still disease
- CACH syndrome
- CADASIL
- Classic galactosemia
- Combined malonic and methylmalonic acidemia
- Congenital lipoid adrenal hyperplasia due to STAR deficency
and 14 more in this range
Rare1–4%
10- Ethylene glycol poisoning
- Hemophagocytic syndrome associated with an infection
- Homocystinuria due to methylene tetrahydrofolate reductase deficiency
- Hyperammonemia due to N-acetylglutamate synthase deficiency
- Lead poisoning
- Meconium aspiration syndrome
- Multiple acyl-CoA dehydrogenase deficiency
- Primary sclerosing cholangitis
and 2 more in this range
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.