GM1 gangliosidosis

A diagnosis of GM1 gangliosidosis (GM1), can be made by either enzyme analysis of the beta-galactosidase enzyme, or by molecular genetic testing of the GLB1 gene. Despite the availability of molecular genetic testing, the mainstay of diagnosis will likely continue to be enzyme activity because of cost and difficulty in interpreting unclear results. However, enzyme activity may not be predictive of carrier status in relatives of affected people. Carrier testing for at-risk family members is done with molecular genetic testing, and is possible if the disease-causing mutations in the family are already known.

The Genetic Testing Registry (GTR) provides information about the labs that offer genetic testing for this condition. The intended audience for the GTR is health care providers and researchers. Therefore, patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

It has been suggested that affected individuals may benefit from physical and occupational therapy. However, we were unable to locate any studies or reports that discuss the use of physical or occupational therapy for affected individuals in the available literature. Furthermore, we were unable to find information about the type of GM1 gangliosidosis, as well as the age group, for which these types of therapies may be beneficial.

Having a family history of GM1 gangliosidosis may mean that certain relatives are at risk to either be affected, be a carrier, or have children that are affected.

For an autosomal recessive condition like GM1 gangliosidosis:

• At conception, each sibling of an affected person has a 25% chance to be affected, a 50% chance to be an asymptomatic carrier, and a 25% chance to be unaffected and not a carrier.
• Once an at-risk sibling is known to be unaffected, the risk for him/her to be a carrier is 2/3 (about 67%).
• A carrier is generally not at risk to have an affected child unless his/her partner is also a carrier.
• Each child of a carrier has a 50% chance to be a carrier.
• While severely affected people with GM1 do not have children, the children of a mildly affected person will always be carriers.
• A person who has not inherited a disease-causing mutation from a parent (i.e. is not a carrier) is not at risk to pass it to his/her children, because the mutation has been eliminated from that lineage.

People with questions about genetic risks for themselves or family members are encouraged to speak with a genetics professional.

The long-term outlook (prognosis) for people with GM1 gangliosidosis (GM1) depends on the type, age of onset, and severity of the condition in each person.

Type 1, also known as the infantile form, is the most severe type of GM1. Children with type 1 usually do not survive past early childhood due to infection and cardiopulmonary failure. Type 2, which includes the late- infantile and juvenile forms, is an intermediate form of the condition. People with type 2 who have late-infantile onset usually survive into mid-childhood, while those with juvenile onset may live into early adulthood. Type 3, known as the adult or chronic form of GM1, is the mildest form of the condition. The age of onset and life expectancy for people with type 3 varies, but life expectancy is usually shortened.