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Type 1 is the most frequent form of GM1 gangliosidosis but the exact prevalence is not known. About 200 cases have been reported to date. Overall prevalence at birth of GM1 gangliosidosis is estimated to be approximately 1:100,000 to 200,000 live births.

The onset of this disorder may be in utero (non immune hydrops fetalis) or by the age of six months. Clinical signs are variable and include arrest/regression of neurological development, hypotonia, visceromegaly, macular cherry-red spots, dysostosis and coarse facial features. Cardiomyopathy may occur.

GM1 gangliosidosis is caused by mutations in the GLB1 gene (3p22.3) coding for beta-galactosidase.

Diagnosis is based on clinical signs although classic signs are not always present at diagnosis. Biochemical and/or molecular genetic tests confirm the diagnosis.

Differential diagnosis includes mucopolysaccharidoses, sphingolipidoses and oligosaccharidoses (see these terms).

Prenatal diagnosis can be performed by analysis of beta-galactosidase activity and/or by GLB1 molecular analysis in either chorionic villus (CV) cells or amniotic fluid cells if mutations are found in an index case.

GM1 gangliosidosis is an autosomal recessive disease. Genetic counseling should be provided to affected families.

Treatment for patients with GM1 gangliosidosis is symptomatic and supportive.

Prognosis is very poor with life-expectancy rarely exceeding 2 years. Causes of death include pneumonia due to recurrent aspiration and cardiopulmonary failure.