GM2-Gangliosidosis, AB variant

GM2-Gangliosidosis, AB variant
GM2-Gangliosidosis, AB variant

Overview Of GM2-Gangliosidosis, AB variant

AB variant GM2-gangliosidosis is a rare hereditary disorder, that systematically destroys nerve cells/ neurons in the central nervous system (CNS). The central nervous system consists of both the brain and spinal cord.

AB variant begins in infancy, before early childhood. Afflicted babies may appear normal until the age of 3 to 6 months. In due time, mental development begins to decline and muscles used for movement weaken. They lose the motor control, necessary for turning over, sitting up, and crawling. These babies likewise develop an exaggerated startle response to loud noises.

As the disease worsens, other symptoms also begin to show. These include:

  • Both vision and hearing loss
  • Continued intellectual/ mental impairment
  • Seizures
  • Paralysis.

A unique symptom of AB variant gangliosidis is the ‘cherry-red spot’. This retinal deformity is only seen during an eye exam, which a qualified ophthalmologist or retinal specialist will perform.

Presently, infants rarely survive past early childhood

Commonly Associated With

  • AB variant
  • Hexosaminidase activator deficiency
  • Tay-Sachs Disease, AB Variant
  • Activator-deficient Tay-Sachs disease
  • Activator Deficiency/GM2 Gangliosidosis
  • GM2 Activator Deficiency Disease
  • GM2 gangliosidosis, type AB

Causes of GM2-Gangliosidosis, AB variant

Mutations of the GM2A gene causesGM2-gangliosidosis, AB variant. The GM2A gene provides the blueprints for making the protein GM2 ganglioside activator. This protein also ensures the normal function of the enzyme beta-hexosaminidase A, which plays a critical role in the efficient functioning of the CNS (brain and spinal cord).

GM2 ganglioside activator protein and Beta-hexosaminidase A are part of the functioning of lysosomes. Lysosomes are structures inside cells that are responsible for breaking down toxins. Inside them, the activator protein binds to GM2 ganglioside and presents it to beta-hexosaminidase A to be broken down and safely reused or removed.

Any aberration of the GM2A gene will unquestionably mess up the ability of the GM2 ganglioside activator, which prevents beta-hexosaminidase A from breaking down GM2 ganglioside. As a result, GM2 ganglioside reaches toxic levels, especially in the CNS. Because the AB variant impairs the function of lysosomes and involves the buildup of GM2 ganglioside, this condition is sometimes referred to as a lysosomal storage disorder.


This is a relatively rare, yet ultimately fatal condition. Worldwide there has only been a handful of cases.  AB variant is inherited. Both parents have only one copy of the mutated gene, but since two are required to trigger this disorder, parents do not typically shows signs.