The GM1 gangliosidoses are caused by a deficiency of beta-galactosidase, with resulting abnormal storage of acidic lipid materials in cells of the central and peripheral nervous systems, but particularly in the nerve cells.

GM1 has three forms: early infantile, late infantile, and adult.

Early infantile GM1

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Symptoms of early infantile GM1 (the most severe subtype, with onset shortly after birth) may include neurodegeneration, seizures, liver and spleen enlargement, coarsening of facial features, skeletal irregularities, joint stiffness, distended abdomen, muscle weakness, exaggerated startle response to sound, and problems with gait.

About half of affected patients develop cherry-red spots in the eye.

Children may be deaf and blind by age 1 and often die by age 3 from cardiac complications or pneumonia.

Late infantile GM1

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Onset of late infantile GM1 is typically between ages 1 and 3 years.

Neurological symptoms include ataxia, seizures, dementia, and difficulties with speech.

Adult GM1

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Onset of adult GM1 is between ages 3 and 30.

Symptoms include muscle atrophy, neurological complications that are less severe and progress at a slower rate than in other forms of the disorder, corneal clouding in some patients, and dystonia (sustained muscle contractions that cause twisting and repetitive movements or abnormal postures).

Angiokeratomas may develop on the lower part of the trunk of the body.

Most patients have a normal size liver and spleen.

Diseases