Are there other forms of Tay-Sachs Disease besides the classical type that affects babies?
The classic infantile type of Tay-Sachs is the most common. However, there are other rare deficiencies of the Hex-A enzyme that sometimes are included under the name of Tay-Sachs disease. These often are referred to as juvenile, chronic and adult-onset forms of Hex-A deficiency. Affected individuals have low levels of the Hex-A enzyme that is missing entirely in the classical, infantile form. This may help explain why symptoms begin later in life and, generally, are less profound than in the classical, infantile Tay-Sachs disease. Children with juvenile Hex-A deficiency develop symptoms between the ages of 2 and 5 that resemble those of the classical, infantile form. Although the course of the disease is slower, death generally occurs by age 15. Symptoms of chronic Hex-A deficiency also may begin by age 5, but are far milder than those that characterize the infantile and juvenile forms. Mental abilities, vision and hearing remain intact; but there may be slurred speech, muscle weakness
