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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed January 2008

What is beta-mannosidosis?

Beta-mannosidosis is a rare inherited disorder affecting the way certain sugar molecules are processed in the body.

Signs and symptoms of beta-mannosidosis vary widely in severity, and the age of onset ranges between infancy and adolescence. Almost all individuals with beta-mannosidosis experience intellectual disability, and some have delayed motor development and seizures. Affected individuals may be extremely introverted, prone to depression, or have behavioral problems such as hyperactivity, impulsivity or aggression.

People with beta-mannosidosis may experience an increased risk of respiratory and ear infections, hearing loss, speech impairment, swallowing difficulties, poor muscle tone (hypotonia), and reduced sensation or other nervous system abnormalities in the extremities (peripheral neuropathy). They may also exhibit distinctive facial features and clusters of enlarged blood vessels forming small, dark red spots on the skin (angiokeratomas).

How common is beta-mannosidosis?

Beta-mannosidosis is believed to be a very rare disorder. Approximately 20 affected individuals have been reported worldwide. It is difficult to determine the specific incidence of beta-mannosidosis, because people with mild or non-specific symptoms may never be diagnosed.

What genes are related to beta-mannosidosis?

Mutations in the MANBA gene cause beta-mannosidosis.

The MANBA gene provides instructions for making the enzyme beta-mannosidase. This enzyme works in the lysosomes, which are compartments that digest and recycle materials in the cell. Within lysosomes, the enzyme helps break down complexes of sugar molecules (oligosaccharides) attached to certain proteins (glycoproteins). Beta-mannosidase is involved in the last step of this process, helping to break down complexes of two sugar molecules (disaccharides) containing a sugar molecule called mannose.

Mutations in the MANBA gene interfere with the ability of the beta-mannosidase enzyme to perform its role in breaking down mannose-containing disaccharides. These disaccharides gradually accumulate in the lysosomes and cause cells to malfunction, resulting in the signs and symptoms of beta-mannosidosis.

Related Gene(s)

Changes in this gene are associated with beta-mannosidosis.


How do people inherit beta-mannosidosis?

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

Where can I find information about diagnosis or management of beta-mannosidosis?

These resources address the diagnosis or management of beta-mannosidosis and may include treatment providers.

  • Genetic Testing Registry: Beta-D-mannosidosis (

You might also find information on the diagnosis or management of beta-mannosidosis in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about beta-mannosidosis?

You may find the following resources about beta-mannosidosis helpful. These materials are written for the general public.

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

What other names do people use for beta-mannosidosis?

  • beta-D-mannosidosis
  • beta-mannosidase deficiency
  • lysosomal beta A mannosidosis
  • lysosomal beta-mannosidase deficiency

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about beta-mannosidosis?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding beta-mannosidosis?

autosomal ; autosomal recessive ; cell ; deficiency ; depression ; disability ; enzyme ; gene ; glycoproteins ; hyperactivity ; hypotonia ; incidence ; inherited ; mannose ; molecule ; motor ; muscle tone ; nervous system ; neuropathy ; oligosaccharides ; peripheral ; peripheral neuropathy ; recessive ; respiratory

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Alkhayat AH, Kraemer SA, Leipprandt JR, Macek M, Kleijer WJ, Friderici KH. Human beta-mannosidase cDNA characterization and first identification of a mutation associated with human beta-mannosidosis. Hum Mol Genet. 1998 Jan;7(1):75-83. (
  • Bedilu R, Nummy KA, Cooper A, Wevers R, Smeitink J, Kleijer WJ, Friderici KH. Variable clinical presentation of lysosomal beta-mannosidosis in patients with null mutations. Mol Genet Metab. 2002 Dec;77(4):282-90. (
  • Gort L, Duque J, Fabeiro JM, Zulaica A, Coll MJ, Chabás A. Molecular analysis in two beta-mannosidosis patients: description of a new adult case. Mol Genet Metab. 2006 Dec;89(4):398-400. Epub 2006 Aug 14. (
  • Molho-Pessach V, Bargal R, Abramowitz Y, Doviner V, Ingber A, Raas-Rothschild A, Ne'eman Z, Zeigler M, Zlotogorski A. Angiokeratoma corporis diffusum in human beta-mannosidosis: Report of a new case and a novel mutation. J Am Acad Dermatol. 2007 Sep;57(3):407-12. Epub 2007 Apr 8. Review. (
  • Uchino Y, Fukushige T, Yotsumoto S, Hashiguchi T, Taguchi H, Suzuki N, Konohana I, Kanzaki T. Morphological and biochemical studies of human beta-mannosidosis: identification of a novel beta-mannosidase gene mutation. Br J Dermatol. 2003 Jul;149(1):23-9. (
  • Zhu M, Lovell KL, Patterson JS, Saunders TL, Hughes ED, Friderici KH. Beta-mannosidosis mice: a model for the human lysosomal storage disease. Hum Mol Genet. 2006 Feb 1;15(3):493-500. Epub 2005 Dec 23. (


The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? ( in the Handbook.

Reviewed: January 2008
Published: February 8, 2016