A type of lysosomal storage disease that is often caused by a deficiency of beta-mannosidase resulting in the accumulation of mannose-containing disaccharides in cells and tissues
Lysosomal storage disease is a collective term for the various metabolic disorders due to defects in lysosomal function resulting in an abnormal accumulation of toxic materials in the cell. One of them is beta-mannosidosis, which is characterized by the accumulation of mannose-containing disaccharides in the lysosomes of cells. Beta-mannosidosis is a metabolic disorder caused by pathological mutation in the gene MANBA. In humans, this gene is located at 4q22-25 and is responsible for the coding of beta-mannosidase. The enzyme helps in the breaking down of complex sugar molecules (oligosaccharides) that are attached to glycoproteins. In particular, beta-mannosidase takes a role in the final step of N-linked glycoprotein oligosaccharide catabolism. The deficiency of this enzyme would therefore affect its function. It then leads to the accumulation of mannose-containing disaccharides within lysosomes of cells. The buildup of these molecules would progress to a disease, particularly beta-mannosidosis. The infantile type is the severe form. Symptoms include neurodegeneration, intellectual disability, hearing loss, angiokeratomas, etc.
The condition is inherited in an autosomal recessive pattern. This means that the individual has two copies of the defective gene and therefore manifests symptoms associated with the disease. A carrier of the disease would have only one copy of the defective gene and therefore may not show symptoms.