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GM1 gangliosidosis

  • What is GM1 gangliosidosis?

    GM1 gangliosidosis is an inherited disorder where certain chemical byproducts accumulate in tissues and organs of the body because they cannot be broken down. This is due to a deficiency of the enzyme called beta-galactosidase. This accumulation causes damage to the tissues and organs, in particular to the brain. Onset of symptoms is broken down into three types. The first type is the earliest onset and most severe outcome. Symptoms usually appear around 6 months of age, when development starts to slow down or there may even be a loss of acquired skills. Affected infants begin to have an exaggerated response to loud noises. Their liver and spleen become enlarged, heart muscles begin to weaken, seizures often occur, and by the end of the year, most infants have lost their vision and hearing. Development of a cherry-red spot on the eye is a unique characteristic of this disorder. As these children grow older, they develop skeletal abnormalities and profound intellectual disability. They may also develop characteristic facial features that are referred to as "coarse". Life expectancy is short, with death by age two to three years old. Type II has a later onset, usually between one and three years of life, or later on as a juvenile of around ten year of age. Many of the symptoms are similar though less rapid in their progression. Life expectancy can extend into the second decade, but is dependent upon the severity of the disease. Symptoms of the final type do not appear until adulthood. These individuals usually develop speech disturbances and an unsteady gait that progressively worsen. Their Intellect deteriorates and they may develop mild skeletal abnormalities. Life expectancy may be shortened. There is no cure for GM1 gangliosidosis but medical surveillance and care may help to improve some symptoms and overall condition of life. GM1 gangliosidosis is caused by pathogenic variants in the GLB1 gene.

  • How is GM1 gangliosidosis inherited?

    GM1 gangliosidosis is inherited in an autosomal recessive manner. This type of inheritance requires the presence of two copies of a pathogenic variant for a person to have the genetic disease. Both parents must be carriers of a pathogenic variant in the gene in order to be at risk to have an affected child. The child must inherit a pathogenic variant from each carrier parent in order to be affected. There is a 1 in 4 chance that a baby will inherit two mutated copies of the gene and be affected when both parents are carriers.

  • What does it mean to be a carrier?

    There are generally no signs or symptoms associated with being a carrier for GM1 gangliosidosis. However, the risk to have a child affected with GM1 gangliosidosis is increased. Testing of reproductive partners is recommended for carriers of GM1 gangliosidosis.

  • How common is GM1 gangliosidosis?

    GM1 gangliosidosis is estimated to occur in 1 in 100,000 to 200,000 newborns worldwide. Type 1 is most common, though Type 3 is more common in the Japanese population.

  • What is analysed?

    Full gene sequencing

AFFECTED SYSTEMS
Brain
Muscle
Liver
Bones
Heart
CARRIER RATES
Ethnicity Detection Rate Carrier Frequency
General Population > 99% 1 in 158