GM1-Gangliosidosis, Type II

Alternative Names

  • Gangliosidosis, Generalized GM1, Juvenile Type
  • Gangliosidosis, Generalized GM1, Type II
  • Gangliosidosis, Generalized GM1, Type 2
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WHO-ICD-10 version:2010

Endocrine, nutritional and metabolic diseases

Metabolic disorders

OMIM Number


Mode of Inheritance

Autosomal recessive

Gene Map Locus



GM1-Gangliosidosis, type 2 is a lysosomal storage disorder characterized by the accumulation of acidic lipid materials such as GM1 ganglioside, oligosaccharides, and the mucopolysaccharide keratan sulfate in the neurons of the central and peripheral nervous systems, resulting in the progressive destruction of these neurons. Patients suffer from developmental regression, progressive psychomotor retardation, ataxia, seizures and dementia.  GM1-Gangliosidosis has three subtypes based on age of onset: type 1 is the severe infantile form of the disorder affecting children at birth or in early infancy, type 2 is the milder form and has a juvenile or late-infantile onset, usually presenting in children aged 1-3 years, while type 3 is the mildest subset, also known as the adult or chronic form of the disorder.

While GM1-Gangliosidosis has an estimated prevalence of about 1 in 100,000 to 200,000 live births, type 2 is the less frequent form, with only about 50 cases reported so far. GM1-Gangliosidosis, Type II follows an autosomal recessive pattern of inheritance and is caused by mutations in the GLB1 gene.

Epidemiology in the Arab World

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Other Reports

Saudi Arabia

Gascon et al. (1992) described two Saudi Arab siblings with GM1 Gangliosidosis type 2.  The sister (age 7 yrs.) and the brother (age 9 yrs.) both presented with developmental arrest, gait disturbance and dementia.  Both were bedridden by 2 years of age and suffered progressive myoclonic epilepsy syndrome with hyperacusis.  CT scans showed global brain atrophy and the patients showed no response to visual or auditory stimuli.  Eventually, spastic quadriparesis led to a decerebrate state.  Bone marrow biopsies revealed sea-blue histiocytes while lysosomal enzyme assays showed normal glucosidase, hexosaminidase and neuraminidase activity but deficient ß-galactosidase activity. The deficiency of ß-galactosidase activity was further confirmed by studying exogenous labelled GM1 ganglioside added to patients’ cells.  Due to the defective lysosomal breakdown of GM1 ganglioside, there was no label fixation seen in the cell pellet.  There was no macular or retinal degeneration, organomegaly or somatic-facial features suggestive of mucopolysaccharidosis.  The siblings had another affected brother with similar complaints.  However, he passed away at the age of 3 years.  They has four other healthy siblings. 

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