Definition

GM1 gangliosidosis and Mucopolysaccharidosis type IVB (Morquio B) result from biallelic variants in the GLB1 gene, which cause beta-galactosidase enzyme deficiency. Variants in the central/5' region of the gene disrupt ganglioside breakdown, causing GM1 gangliosidosis with neurodegeneration, while a subgroup of variants near the 3' end leads to the Morquio B phenotype, characterized by keratan sulfate accumulation without neurodegeneration.

Gene/region examined

GLB1 - Exon 1, GLB1 - Exon 2, GLB1 - Exon 3, GLB1 - Exon 4, GLB1 - Exon 5, GLB1 - Exon 6, GLB1 - Exon 7, GLB1 - Exon 8, GLB1 - Exon 9, GLB1 - Exon 10, GLB1 - Exon 11, GLB1 - Exon 12, GLB1 - Exon 13, GLB1 - Exon 14, GLB1 - Exon 15, GLB1 - Exon 16

Method

Sequence analysis

Accepted sample types

EDTA blood, AF, CVS

Inheritance

Hereditary, autosomal recessive.

Related Tests

Inheritance Patterns

Describes how a genetic condition is passed on within a family. There are five main patterns

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Carrier (Heterozygous / Homozygous)

Why it matters: In autosomal recessive inheritance, when each parent is a carrier (while both appear healthy), the chance of their child being born with the disease is 25% in each

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VUS (Variant of Uncertain Significance)

This is the situation where the test has detected a change in the DNA, but the role of this change in the development of disease is unconfirmed.

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How to Read a Genetic Test Result (Positive / Negative / VUS)

A genetic test result falls into three main categories

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Types of Genetic Tests

A genetic test is a type of medical test that detects changes in genes, chromosomes or proteins. Today there are more than 77,000 genetic tests available.

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