Skip to Main Content




  • B variant GM2 gangliosidosis

  • GM2 gangliosidosis, type 1

  • HexA deficiency

  • Hexosaminidase A deficiency

  • Hexosaminidase alpha-subunit deficiency (variant B)

  • Sphingolipidosis, Tay-Sachs

  • TSD




  • 330.1 Cerebral lipidoses




  • E75.02 Tay–Sachs disease




  • 5B Impaired Neuromotor Development

  • 5C Impaired Motor Function and Sensory Integrity Associated with Nonprogressive Disorders of the Central Nervous System—congenital origin or acquired in infancy or childhood



A 9-month-old male child is referred to physical therapy for developmental delay. The parents report an uneventful pregnancy and delivery. The child rolls consecutively as the primary method of mobility and props with his arms for balance when in sitting. Over the next few weeks, the child sees ophthalmologist with a report of cherry red spots on his macula, an MRI indicates cortical atrophy, and geneticist diagnoses him with Tay–Sachs disease. Over the next few months, the infant begins to lose gross motor function such as rolling and prop sitting.




  • Progressive autosomal recessive genetic disorder.

  • Infant lacks protein, beta-hexosaminidase A (Hex A), that prevents the accumulation of the lipid, ganglioside GM-2, thus, causing damage to brain cells.

Essentials of Diagnosis

  • Genetic defect of chromosome 15

  • Sandhoff disease: Unable to make (Hexa A or B)

General Considerations

  • Categories

    • Infantile: Most common; symptoms appear between 3 to 6 months of age

    • Juvenile: Symptoms begin between 2 and 5 years of age

    • Adult: Symptoms begin during adolescence or as young adult

FIGURE 255-1

“Cherry-red” spot in the eye of a Tay–Sachs patient. (From

Graphic Jump Location

  • 1 in every 27 Ashkenazi Jewish people4

  • 1 out of 250 people5

  • 1 in every 27 French Canadian, Louisiana Cajuns, Ashkenazi Jewish people5

  • 1 in every 50 or 150 British Isles or Irish people5

  • Equally affects males and females





  • Deafness

  • Blindness

  • Loss of gag reflex

  • Difficulty swallowing

  • Muscle weakness

  • Hypotonia

  • Seizures

  • Paralysis

  • Regression in gross motor and fine motor skills

  • Cherry-red spot on eyes

Functional Implications

  • Progressive muscle weakness resulting in decline in gross motor and fine motor skills such as inability to sit, ambulate or feed self



Laboratory Tests

  • Performed early in pregnancy by amniocentesis or chorionic villus sampling

  • Blood test for hexosaminidase A (hex A) levels

  • Blood from the vein of the umbilical cord

Diagnostic Procedure

  • DNA analysis, (Hexa) ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessPhysiotherapy Full Site: One-Year Subscription

Connect to the full suite of AccessPhysiotherapy content and resources including interactive NPTE review, more than 500 videos, Anatomy & Physiology Revealed, 20+ leading textbooks, and more.

$595 USD
Buy Now

Pay Per View: Timed Access to all of AccessPhysiotherapy

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.