B variant GM2 gangliosidosis
GM2 gangliosidosis, type 1
Hexosaminidase A deficiency
Hexosaminidase alpha-subunit deficiency (variant B)
PREFERRED PRACTICE PATTERNS3
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.
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
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
MEANS OF CONFIRMATION OR DIAGNOSIS
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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