Beta-mannosidase is an enzyme that catalyzes the hydrolysis of terminal, non-reducing beta-D-mannose residues in beta-D-mannosides. This enzyme plays a role in the lysosomal degradation of the N-glycosylprotein glycans. Mutations in the gene encoding for beta-mannosidase would interfere in its ability to perform its role, hence, resulting in the accumulation of the mannose-containing disaccharides in lysosomes and cause cells to malfunction. This inborn error of metabolism is called beta-mannosidosis. Therefore, DEFICIENCY of the enzyme is associated with beta-mannosidosis. Symptoms may include intellectual disability, hearing loss, speech impairment, swallowing difficulties, poor muscle tone, behavioral problems (hyperactivity, or impulsivity), and peripheral neuropathy.