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

Mannose-binding lectin deficiency

Reviewed March 2012

What is mannose-binding lectin deficiency?

Mannose-binding lectin deficiency is a condition that affects the immune system. People with this condition have low levels of an immune system protein called mannose-binding lectin in their blood. These individuals are prone to recurrent infections, including infections of the upper respiratory tract and other body systems. People with this condition may also contract more serious infections such as pneumonia and meningitis. Depending on the type of infection, the symptoms caused by the infections vary in frequency and severity.

Infants and young children with mannose-binding lectin deficiency seem to be more susceptible to infections, but adults can also develop recurrent infections. In addition, affected individuals undergoing chemotherapy or taking drugs that suppress the immune system are especially prone to infections.

How common is mannose-binding lectin deficiency?

Mannose-binding lectin deficiency is thought to affect approximately 5 to 10 percent of people worldwide; however, many affected individuals have no signs or symptoms related to low mannose-binding lectin levels. The condition is more common in certain populations, such as sub-Saharan Africans.

What genes are related to mannose-binding lectin deficiency?

Relatively common mutations in the MBL2 gene can lead to mannose-binding lectin deficiency. This gene provides instructions for making a protein that assembles into a complex called mannose-binding lectin. Functional mannose-binding lectins are made up of two to six protein groups called trimers, which are each composed of three of the protein pieces (subunits) produced from the MBL2 gene.

Mannose-binding lectin plays an important role in the body's immune response by attaching to foreign invaders such as bacteria, viruses, or yeast and turning on (activating) the complement system. The complement system is a group of immune system proteins that work together to destroy foreign invaders (pathogens), trigger inflammation, and remove debris from cells and tissues. Mannose-binding lectin can also stimulate special immune cells to engulf and break down the attached pathogen.

Disease-associated mutations in the MBL2 gene can reduce the production of the mannose-binding lectin subunit or eliminate the subunit's ability to assemble into functional mannose-binding lectin. A decrease in the availability of the normal subunit protein may lead to a reduction of the functional mannose-binding lectin in blood. With decreased levels of mannose-binding lectin, the body does not recognize and fight foreign invaders efficiently. Consequently, infections can be more common in people with this condition.

However, not everyone with a change in the MBL2 gene has decreased levels of mannose-binding lectin, and not everyone with decreased protein levels is prone to infection. Researchers believe that a number of factors, including other genetic and environmental factors, are involved in the development of mannose-binding lectin deficiency and susceptibility to infection.

Related Gene(s)

Changes in this gene are associated with mannose-binding lectin deficiency.

  • MBL2

How do people inherit mannose-binding lectin deficiency?

The inheritance pattern of mannose-binding lectin deficiency is unclear. Some reports show that having a disease-associated mutation in one copy of the MBL2 gene in each cell can lead to the condition, while other reports state that a mutation in both copies of the gene is necessary. It is important to note that people inherit an increased risk of developing mannose-binding lectin deficiency, not the condition itself. Not all people who inherit mutations in this gene will develop the condition.

Where can I find information about diagnosis or management of mannose-binding lectin deficiency?

These resources address the diagnosis or management of mannose-binding lectin deficiency and may include treatment providers.

  • Genetic Testing Registry: Mannose-binding protein deficiency (

You might also find information on the diagnosis or management of mannose-binding lectin deficiency 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 mannose-binding lectin deficiency?

You may find the following resources about mannose-binding lectin deficiency 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 mannose-binding lectin deficiency?

  • mannose-binding lectin protein deficiency
  • mannose-binding protein deficiency
  • MBL2 deficiency
  • MBL deficiency
  • MBP 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 mannose-binding lectin deficiency?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding mannose-binding lectin deficiency?

bacteria ; cell ; chemotherapy ; deficiency ; gene ; immune response ; immune system ; infection ; inflammation ; inherit ; inheritance ; inheritance pattern ; mannose ; mutation ; pathogen ; pneumonia ; protein ; respiratory ; subunit ; susceptibility

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


  • Arora M, Munoz E, Tenner AJ. Identification of a site on mannan-binding lectin critical for enhancement of phagocytosis. J Biol Chem. 2001 Nov 16;276(46):43087-94. Epub 2001 Aug 30. (
  • Bouwman LH, Roep BO, Roos A. Mannose-binding lectin: clinical implications for infection, transplantation, and autoimmunity. Hum Immunol. 2006 Apr-May;67(4-5):247-56. Epub 2006 Apr 17. Review. (
  • Degn SE, Jensenius JC, Thiel S. Disease-causing mutations in genes of the complement system. Am J Hum Genet. 2011 Jun 10;88(6):689-705. doi: 10.1016/j.ajhg.2011.05.011. Review. (
  • Martin P, Lerner A, Johnson L, Lerner DL, Haraguchi S, Good RA, Day NK. Inherited mannose-binding lectin deficiency as evidenced by genetic and immunologic analyses: association with severe recurrent infections. Ann Allergy Asthma Immunol. 2003 Oct;91(4):386-92. (
  • Ram S, Lewis LA, Rice PA. Infections of people with complement deficiencies and patients who have undergone splenectomy. Clin Microbiol Rev. 2010 Oct;23(4):740-80. doi: 10.1128/CMR.00048-09. Review. (
  • Turner MW. The role of mannose-binding lectin in health and disease. Mol Immunol. 2003 Nov;40(7):423-9. Review. (
  • Weis WI, Drickamer K, Hendrickson WA. Structure of a C-type mannose-binding protein complexed with an oligosaccharide. Nature. 1992 Nov 12;360(6400):127-34. (


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: March 2012
Published: February 1, 2016