GM1 Gangliosidosis is a lysosomal storage disorder that affects the body’s ability to break down certain fats and sugar-containing molecules. Specifically, the disorder is caused by a problem in the GLB1 gene, which provides instructions for making the enzyme beta-galactosidase. This enzyme is required to break down a fatty substance called GM1 ganglioside, as well as other complex molecules found in cells. When beta-galactosidase does not function properly, GM1 ganglioside and related substances accumulate inside lysosomes. Lysosomes are structures within cells responsible for breaking down waste materials. The buildup of these substances causes progressive damage to cells and tissues, particularly in the brain, spinal cord, liver, bones, and other organs. Over time, this leads to severe neurological and systemic complications. GM1 gangliosidosis exists as a spectrum of disease severity, depending on the amount of residual enzyme activity present.

The signs and symptoms of GM1 gangliosidosis vary depending on the age of onset and severity, but symptoms generally begin in infancy or early childhood and worsen progressively. Children may develop: • Developmental delay or regression • Weak muscle tone (hypotonia) • Difficulty feeding and poor weight gain • Seizures Other features include: • Enlargement of the liver and spleen (hepatosplenomegaly) • Abnormal bone development and skeletal deformities • Coarse facial features • Clouding of the cornea • Cherry-red spot in the retina • Progressive vision and hearing loss • Frequent respiratory infections In severe infantile forms, neurological decline progresses rapidly, leading to loss of motor skills, inability to sit or swallow, and severe intellectual disability. Life expectancy in these cases is often limited to early childhood. Milder juvenile or adult forms progress more slowly but still lead to significant disability.

GM1 gangliosidosis is caused by mutations in the GLB1 gene. The condition follows an autosomal recessive inheritance pattern.

Diagnosis is based on a combination of: • Clinical examination and symptom recognition • Enzyme testing showing reduced beta-galactosidase activity • Genetic testing confirming mutations in the GLB1 gene • Imaging studies and laboratory findings supporting neurodegeneration Prenatal diagnosis is possible when the familial mutation is known.

There is currently no cure for GM1 gangliosidosis. Treatment focuses on supportive and palliative care. Management may include: • Seizure control • Nutritional and feeding support • Physiotherapy and occupational therapy • Respiratory support • Management of infections Experimental therapies, including gene therapy and substrate reduction therapy, are under investigation.