Rare diseases · Sign or symptom
Hypsarrhythmia
HP:0002521
What it means
Hypsarrhythmia is abnormal interictal high amplitude waves and a background of irregular spikes. There is continuous (during wakefulness), high-amplitude (>200 Hz), generalized polymorphic slowing with no organized background and multifocal spikes demonstrated by electroencephalography (EEG).
Rare diseases that can present with this46
Very common80–99%
5Common30–79%
13- ALG13-CDG
- ALG2-CDG
- Blepharophimosis-intellectual disability syndrome, Verloes type
- CDKL5-deficiency disorder
- DPAGT1-CDG
- Early infantile developmental and epileptic encephalopathy
- Isolated lissencephaly type 1 without known genetic defects
- Lafora disease
- MFF-related encephalopathy due to mitochondrial and peroxisomal fission defect
- Neurodegeneration due to 3-hydroxyisobutyryl-CoA hydrolase deficiency
- PLAA-associated neurodevelopmental disorder
- Severe neurodevelopmental disorder with feeding difficulties-stereotypic hand movement-bilateral cataract
- Sporadic Creutzfeldt-Jakob disease
Sometimes5–29%
26- 3-hydroxy-3-methylglutaric aciduria
- 3-methylglutaconic aciduria type 9
- 6-pyruvoyl-tetrahydropterin synthase deficiency
- Combined oxidative phosphorylation defect type 39
- DEND syndrome
- DK1-CDG
- Early-onset epileptic encephalopathy-cortical blindness-intellectual disability-facial dysmorphism syndrome
- Early-onset progressive encephalopathy-hearing loss-pons hypoplasia-brain atrophy syndrome
and 18 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
Also called: Hypsarrhythmia by EEG
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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.