Tay–Sachs disease
| Tay–Sachs disease | |
|---|---|
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| Cherry-red spot as seen in Tay–Sachs disease: the fovea's center appears bright red because it is surrounded by a milky halo. | |
| Classification and external resources | |
| Specialty | Medical genetics |
| ICD-10 | E75.0 |
| ICD-9-CM | 330.1 |
| OMIM | 272800 272750 |
| DiseasesDB | 12916 |
| MedlinePlus | 001417 |
| eMedicine | ped/3016 |
| Patient UK | Tay–Sachs disease |
| MeSH | D013661 |
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 begins around seven 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.
The disease is named after the British ophthalmologist Waren Tay, who in 1881 first described a symptomatic red spot on the retina of the eye; and after the American neurologist Bernard Sachs of Mount Sinai Hospital, who described in 1887 the cellular changes of Tay–Sachs disease and noted an increased disease prevalence in Ashkenazi Jews.
Research in the late 20th century demonstrated that Tay–Sachs disease is caused by a genetic mutation in the HEXA gene on chromosome 15. A large number of HEXA mutations have been discovered, and new ones are still being reported. These mutations reach significant frequencies in specific populations. French Canadians of southeastern Quebec have a carrier frequency similar to that seen in Ashkenazi Jews, but carry a different mutation. Cajuns of southern Louisiana carry the same mutation that is seen most commonly in Ashkenazi Jews. HEXA mutations are rare and are most seen in genetically isolated populations. Tay–Sachs can occur from the inheritance of either two similar, or two unrelated, causative mutations in the HEXA gene.
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