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# Tay–Sachs disease

In Tay–Sachs disease a lipid called GM2 builds up in neurons; the baby stops progressing, loses skills and loses sight.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Macula](https://durgical.com/en/anatomy/macula/)
- [Retina](https://durgical.com/en/anatomy/retina/)
- [White matter](https://durgical.com/en/anatomy/white-matter-of-telencephalon/)
- [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/)
- [Cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/)
- [Optic nerve](https://durgical.com/en/anatomy/optic-nerve/)
- [Thalamus](https://durgical.com/en/anatomy/thalamus/)

## In biochemistry

- [Lysosomal ganglioside breakdown: Step 2 · β-Hexosaminidase A (HEXA α + HEXB β subunits) with the GM2 activator](https://durgical.com/en/biochemistry/pathways/lysosomal-ganglioside-breakdown/#paso-2)
- [Sphingolipids and sphingolipidoses](https://durgical.com/en/biochemistry/topics/sphingolipids-and-sphingolipidoses/)
- [Lysosomal storage diseases](https://durgical.com/en/biochemistry/topics/lysosomal-storage-diseases/)
- [GM2 ganglioside](https://durgical.com/en/biochemistry/molecules/gm2-ganglioside/)
- [Hexosaminidase A (β-hexosaminidase A)](https://durgical.com/en/biochemistry/enzymes/hexosaminidase-a/)
- [Hexosaminidase B (β-hexosaminidase B)](https://durgical.com/en/biochemistry/enzymes/hexosaminidase-b/)

## In histology

- [Organelles: nucleus, ER, Golgi, mitochondria, lysosomes, peroxisomes](https://durgical.com/en/histology/organelles-nucleus-er-golgi-mitochondria-lysosomes-peroxisomes/)

## Why it happens

- [How a single gene causes disease: enzymes, receptors and structural proteins](https://durgical.com/en/general-pathology/how-a-single-gene-causes-disease-enzymes-receptors-and-structural-proteins/)
- [Intracellular accumulations: cholesterol, proteins, hyaline, glycogen](https://durgical.com/en/general-pathology/intracellular-accumulations-cholesterol-proteins-hyaline-glycogen/)

## What it is

An autosomal recessive GM2 gangliosidosis caused by deficiency of the α subunit of hexosaminidase A (HEXA gene). It affects almost only the [nervous system](https://durgical.com/en/anatomy/system/nervous-system/).

## Who gets it

Very rare in the general population. The variants are more common in Ashkenazi Jews, French-Canadian communities of Quebec, the Amish and the Cajun people of Louisiana; carrier screening has greatly reduced cases in these groups.

## Causes

- Biallelic variants of the HEXA gene (autosomal recessive)

## Risk factors

- Carrier parents
- Belonging to a population with a high carrier frequency

## Pathophysiology

Without hexosaminidase A, GM2 ganglioside from neuronal membranes is not converted to GM3 and fills neuronal lysosomes (membranous cytoplasmic bodies). Neurons swell, lose function and die. In the [retina](https://durgical.com/en/anatomy/retina/), lipid-laden ganglion cells look whitish around the fovea, which lacks them and stands out red (cherry-red spot). There is no major visceral storage, so the [liver](https://durgical.com/en/anatomy/liver/) and [spleen](https://durgical.com/en/anatomy/spleen/) do not enlarge.

## Classification

- Infantile (classic): onset at 3–6 months, the most common
- Juvenile: onset in childhood, slower course
- Late-onset or adult: weakness, ataxia and psychiatric symptoms

## Symptoms and signs

- Exaggerated startle to noise
- Loss of motor skills already gained (head control, sitting)
- Hypotonia that later turns into spasticity
- Progressive loss of vision
- Seizures
- Enlarging head (macrocephaly)

## Red flags

- An infant losing developmental milestones
- Hard-to-control seizures
- Swallowing difficulty with aspiration risk

## Diagnosis

**Clinical**
An infant with developmental regression, exaggerated startle and a cherry-red spot on fundoscopy, without hepatosplenomegaly.

**Tests**
Low hexosaminidase A activity with normal or high total hexosaminidase in serum or leukocytes; HEXA gene testing; electroencephalogram if there are seizures.

**Imaging**
Brain MRI with [white matter](https://durgical.com/en/anatomy/white-matter-of-telencephalon/) and thalamic changes and, later, atrophy; CT with hyperdense thalami.

## Treatment

**Acute**
Management of seizures and aspiration pneumonia.

**Medical**
No treatment stops the disease; anticonvulsants and control of drooling and spasticity are used. Gene therapy is under investigation.

**Rehabilitation**
Physiotherapy, swallowing therapy and nutritional support (sometimes a gastrostomy tube).

**Conservative**
Palliative care and family support, with genetic counselling.

## Complications

- Aspiration pneumonia
- Status epilepticus
- Blindness
- Malnutrition

## Prognosis

The infantile form usually leads to death between ages 2 and 5. Juvenile and adult forms progress more slowly.

## Prevention

- Carrier screening in at-risk populations
- Genetic counselling and prenatal diagnosis when both parents are carriers

## Test yourself

Think of the answer, then tap the question to see it.

## Which enzyme is missing in Tay–Sachs disease?

Hexosaminidase A, from variants in the HEXA gene (α subunit).

## Why does Tay–Sachs not cause hepatosplenomegaly, unlike Niemann–Pick?

GM2 turns over mainly in neurons; there is no major visceral storage.

## Which fundoscopic finding is typical of the infantile form?

A cherry-red spot at the macula.

## Which early sign stands out in an infant with Tay–Sachs?

An exaggerated startle to noise, before motor regression.

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## Related conditions

- [Niemann–Pick disease](https://durgical.com/en/conditions/niemann-pick-disease/)
- [Epilepsy and seizures](https://durgical.com/en/conditions/epilepsy-and-seizures/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Tay-Sachs disease: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/tay-sachs-disease/) (MedlinePlus, US National Library of Medicine, 2026); [HEXA gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/hexa/) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Source: https://durgical.com/en/conditions/tay-sachs-disease/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/tay-sachs-disease/