Tay Sachs disease:
Tay-Sachs disease (also known as GM2 gangliosidosis or hexosaminidase A deficiency) is a rare autosomal recessive genetic disorder. In its most common variant (known as infantile Tay Sachs disease), it causes a progressive deterioration of nerve cells and of mental and physical abilities that commences around six months of age and usually results in death by the age of four. The disease occurs when harmful quantities of cell membrane components known as gangliosides accumulate in the brain’s nerve cells, eventually leading to the premature death of the cells. A ganglioside is a form of sphingolipid, which makes Tay Sachs disease a member of the sphingolipidoses. There is no known cure or treatment for Tay Sachs disease.
Signs and symptoms:
Tay-Sachs disease is classified into several forms, which are differentiated based on the onset age of neurological symptoms.
- Infantile Tay Sachs disease. Infants with Tay Sachs disease appear to develop normally for the first six months after birth. Then, as neurons become distended with gangliosides, a relentless deterioration of mental and physical abilities begins. The child becomes blind, deaf, unable to swallow, atrophied, and paralytic. Death usually occurs before the age of four.
- Juvenile Tay Sachs disease. Juvenile Tay Sachs disease is rarer than other forms of Tay Sachs, and usually is initially seen in children between two and ten years old. People with Tay–Sachs disease develop cognitive and motor skill deterioration, dysarthria, dysphagia, ataxia, and spasticity. Death usually occurs between the age of five to fifteen years.
- Adult/Late-Onset Tay Sachs disease. A rare form of this disease, known as Adult-Onset or Late-Onset Tay Sachs disease, usually has its first symptoms during the 30s or 40s. In contrast to the other forms, late-onset Tay Sachs disease is usually not fatal as the effects can stop progressing. It is frequently misdiagnosed. It is characterized by unsteadiness of gait and progressive neurological deterioration. Symptoms of late onset Tay Sachs – which typically begin to be seen in adolescence or early adulthood – include speech and swallowing difficulties, unsteadiness of gait, spasticity, cognitive decline, and psychiatric illness, particularly a schizophrenia-like psychosis. People with late-onset Tay Sachs may become full-time wheelchair users in adulthood.
Deficient enzyme:
- Hexosaminidase A
Accumulated substrate:
- GM2 ganglioside
Mode of inheritance:
- Autosomal recessive