What is Gangliosidosis GM2 Type I (Tay-Sachs Disease)?
GM2-gangliosidosis type I (amaurotic idiocy of the Tay – Sachs, Tay – Sachs disease) occurs mainly among Ashkenazi Jews, the frequency of heterozygous gene carriers among this ethnic group is 1: 27.
Causes of Gangliosidosis GM2 Type I (Tay-Sachs Disease)
The amavrotic idiocy of Tay – Saks (GM2-gangliosidosis, type I) develops due to insufficient activity of the enzyme hexosaminidase A and the increased activity of hexosaminidase B.
Pathogenesis during Gangliosidosis GM2 Type I (Tay-Sachs Disease)
Violation of the splitting of GM2-gangliosides as a result of deficiency of the enzyme hexosaminidase A leads to its accumulation in the brain, to a lesser extent in the internal organs. The cytoplasm of neurons overflows with GM2 ganglioside, resulting in central demyelination. If GM2 ganglioside is normally present in trace amounts in brain tissue, it is 6-12% of dry mass in Tay-Sachs disease. In the later stages, megaloencephaly develops due to astrocyte proliferation. At the same time, the amount of cerebroside and sulfatide in the brain decreases sharply.
Symptoms of Gangliosidosis GM2 Type I (Tay-Sachs Disease)
During the first 4-6 months of life, the child develops normally, begins to sit, crawl, smile. There is an increased reaction to external stimuli (noise, light) – from fright to myoclonic seizures. By 6 months, there is hypotension. Since the second year of life, the disturbance of motor and intellectual development has been rapidly progressing. Feeding difficulties due to impaired swallowing. Generalized atonic paralysis develops. After 1-1 / 2 years, deafness, blindness, convulsions progress, muscle tone increases until spastic paralysis appears, up to decerebral rigidity. Many patients describe a “doll” face: pale skin, light blush, long eyelashes, good hair. In 90% of cases in the fundus is determined by the symptom of a cherry seed. Sick children die in the second year of life.
Diagnosis of Gangliosidosis GM2 Type I (Tay-Sachs Disease)
The clinical diagnosis of amaurotic idiocy is based on data from the clinical picture of the disease, characteristic changes in the fundus and determination of the activity of a specific enzyme.