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CONDITION/DISORDER SYNONYMS

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  • B variant GM2 gangliosidosis

  • GM2 gangliosidosis, type 1

  • HexA deficiency

  • Hexosaminidase A deficiency

  • Hexosaminidase alpha-subunit deficiency (variant B)

  • Sphingolipidosis, Tay-Sachs

  • TSD

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ICD-9-CM CODE1

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  • 330.1 Cerebral lipidoses

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ICD-10-CM CODE2

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  • E75.02 Tay–Sachs disease

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PREFERRED PRACTICE PATTERNS3

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  • 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

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PATIENT PRESENTATION

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.

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KEY FEATURES

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Description
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  • 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.

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Essentials of Diagnosis
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  • Genetic defect of chromosome 15

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

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General Considerations
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  • 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

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FIGURE 255-1

“Cherry-red” spot in the eye of a Tay–Sachs patient. (From http://www.nei.nih.gov/resources/eyegene.asp.)

Graphic Jump Location
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Demographics
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  • 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

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CLINICAL FINDINGS

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SIGNS AND SYMPTOMS

  • 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

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

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MEANS OF CONFIRMATION OR DIAGNOSIS

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Laboratory Tests
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  • 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

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Diagnostic Procedure
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  • DNA analysis, (Hexa) ...

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