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Start free with EleplanTay-Sachs disease
ORPHA:845Disease
Also called Beta-hexosaminidase subunit alpha deficiency · GM2 gangliosidosis, Tay-Sachs variant · GM2 gangliosidosis, hexosaminidase A deficiency variant · HEXA disorder
What it is
A rare autosomal recessive lysosomal disease characterized by accumulation of GM2 gangliosides in the nervous system due to hexosaminidase A deficiency as a consequence of biallelic pathogenic variants in the HEXA gene.
Key facts
- Prevalence
- 1-9 / 1 000 000 (at birth)
- Age of onset
- All ages
- Inheritance
- Autosomal recessive
- Classified as
- Disease
Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.
Signs and symptoms
Very common80–99%
6- Abnormal enzyme/coenzyme activity
- Abnormality of glycolipid metabolismDiagnostic criterion
- GM2-ganglioside accumulationDiagnostic criterion
- Muscle weakness
- Progressive spasticity
- Skeletal muscle atrophy
Common30–79%
24- Abnormal thalamic MRI signal intensity
- Aspiration pneumonia
- Atypical behavior
- Cherry red spot of the macula
- Clumsiness
- Developmental regression
- Difficulty climbing stairs
- Distal muscle weakness
- Dysarthria
- Dysphagia
- Fasciculations
- Frequent falls
- Gait disturbance
- Gliosis
- Hyperreflexia
- Hypointensity of cerebral white matter on MRI
- Incoordination
- Lower limb muscle weakness
- Muscle spasm
- Poor fine motor coordination
- Postural instability
- Quadriceps muscle atrophy
- Short attention span
- Visual impairment
Sometimes5–29%
33- Abnormality of eye movement
- Absent speech
- Ankle clonus
- Anxiety
- Blindness
- Cerebellar atrophy
- Depression
- Distal upper limb muscle weakness
and 25 more in this range
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
Genes reported in subtypes
Orphanet records this gene on 3 more specific entries under this disorder, not on this entry itself:
A well-studied disease is usually split into subtypes, and the gene is curated on whichever one the evidence belongs to. Open a subtype to see which gene goes with it.
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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