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Alpha-Mannosidosis

Alpha-mannosidosis, a glycoproteinosis, is due to a genetic defect of the lysosomal enzyme alpha-mannosidase that is responsible for the hydrolysis of glycoprotein carbohydrate moieties. The decreased activity of this enzyme leads to accumulation of oligosaccharides in several cells and organs. Alpha-mannosidosis is a slowly progressive disorder that shows a broad phenotypic variability. Clinical features include hearing impairment, skeletal abnormalities, impairment of mental function, sometimes periods of psychosis. In addition, muscular weakness and ataxia are observed. In the first decade of life recurrent infections occur due to an immune defect.

Etiology: Deficiency of alpha-mannosidase
Gene: MAN2B1 Gene
Mode of inheritance: Autosomal recessive
Phenotypes:

Infantile Form
Milder Form

Leading symptoms:

Infantile form
(Age of onset: infancy)

Severe CNS manifestations
Severe immune deficiency
Hepatosplenomegy

Milder form
(Age of onset: childhood, adolescence)

Facial dysmorphia
Dysostosis multiplex
Hearing impairment
Immune deficiency
Psychomotor development delay
Cognitive impairment
Ataxia
Psychatric symptoms
Hepatosplenomegaly

Diagnostics:

Measurement of the activity of alpha-mannosidase in serum
Molecular genetic analysis of MAN2B1-Gene

Therapy:
Velmanase alfa (Lamzede®)