Definition:
Juvenile Hexosaminidase A Deficiency is caused by the absence of a vital enzyme called hexosaminidase A (Hex-A). Without Hex-A, a fatty substance or lipid called GM2 ganglioside accumulates abnormally in cells, especially in the nerve cells of the brain. Gangliosides need to be biodegraded rapidly in early life as the brain develops. This ongoing accumulation causes progressive damage to the cells, similar to that which occurs in Tay-Sachs Disease.

Symptoms:
Juvenile Hexosaminidase A Deficiency progresses more slowly and later than Tay-Sachs disease, with symptoms appearing between the ages of two and five.  Juvenile hexosaminidase A deficiency typically begins with ataxia between two and 10 years of age.  Speech and mental cognition begins to deteriorate at this time. By the age of 10, seizures and muscle spasticity are typically present.  Loss of vision occurs much later than in the acute infantile form of the disease, and optic atrophy and retinitis pigmentosa may also be seen. A vegetative state develops by 10 to 15 years of age. In some cases, the disease pursues a particularly aggressive course, culminating in death in two to four years from the onset of symptoms.

Inheritance Pattern:
Juvenile Hexosaminidase A Deficiency is an autosomal recessive disorder.

Diagnosis and Testing:
Patients and carriers of Juvenile Hexosaminidase A Deficiency can be identified by a simple blood test that measures the enzymatic activity of beta-hexosaminidase A in blood or tissue samples.

Carrier detection can be performed for males, females, and for pregnant females to determine carrier status of Juvenile Hexosaminidase A Deficiency. A measure of the enzyme hexosaminidase A (Hex-A) is taken using white blood cells or blood samples. It is a highly accurate procedure for determining one’s carrier status.

Life Expectancy:
Life expectancy of Juvenile Hexosaminidase A Deficiency is between 10 and 15 years of age.

Treatment:
There is no cure or effective treatment for Juvenile Hexosaminidase A Deficiency. Anticonvulsant medicine can help to control seizures. Other treatment options include adequate nutrition and hydration, and techniques to keep the airway open.

Enzyme replacement and gene therapies are being investigated as possible treatments to slow or prevent the progression of Juvenile Hexosaminidase A Deficiency.