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Genetic and Rare Diseases Information Center (GARD)

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Mannose-binding lectin protein deficiency


* Not a rare disease
Other Names for this Disease
  • Mannose-binding protein deficiency
  • MBL deficiency
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Your Question

My wife has been diagnosed with MBL deficiency. Can you provide us with information on this condition?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is mannose-binding lectin protein (MBL) deficiency?

Mannose-binding lectin protein (MBL) deficiency is a complement component deficiency that alters the function of the body's immune system. This condition usually causes frequent and sometimes severe infections in infants and young children.[1] This deficiency can occur as a result of one or more variations in the MBL2 gene, which codes for the MBL protein. A lack of this protein can cause this condition, but is likely further influenced by other genetic and environmental factors.[2]
Last updated: 4/9/2012

What causes mannose-binding lectin protein (MBL) deficiency?

MBL deficiency can occur as a result of one or more variations in the MBL2 gene, which codes for the MBL protein. A lack of this protein can cause this condition, but it is likely further influenced by other genetic and environmental factors that are currently poorly understood.[2] 

The mannose-binding lectin (MBL) protein is excreted by the liver and is part of our innate immune defense. This protein binds to sugars on the surface of microorganisms to signal their destruction and triggers one of the major complement cascades called the “mannose-binding lectin (MBL) pathway.” Complement cascades are made up of proteins that work together to destroy bacteria and other antigens. The mannose binding protein circulates in the blood in an inactive form. When it is activated it sets in motion a domino effect where each component of the mannose-binding lectin pathway takes its turn in a precise chain of steps. The end products from the cascade are able to destroy invading bacteria and other antigens.[3] 

More information on immune system responses can be found at the following link from MedlinePlus, the National Library of Medicine Web site designed to help you research your health questions.
Last updated: 4/9/2012

What are the signs and symptoms of mannose-binding lectin protein (MBL) deficiency?

Individuals with MBL deficiency are prone to recurrent infections, including infections of the upper respiratory tract and other body systems. Affected individuals may also contract more serious infections such as pneumonia and meningitis. The signs and symptoms associated with MBL deficiency vary among affected individuals; symptoms may depend upon the type of infections present as well as their frequency and severity.[4]

Infants and young children with MBL deficiency seem to be more susceptible to infections, but adults can also develop recurrent infections.[4] Other individuals more susceptible to infection include cancer patients undergoing chemotherapy and organ-transplant patients receiving immunosuppressive drugs (particularly recipients of liver transplants).[5]

There has been much research regarding the role of MBL deficiency in increasing the risk for complications such as infections in those who have both MBL deficiency and other conditions, such as cystic fibrosis; autoimmune diseases such as rheumatoid arthritis and lupus; AIDS; atherosclerosis; and people on chemotherapy for the treatment of blood cancers (e.g., leukemia, lymphoma) and other blood disorders (e.g., myelodysplastic syndromes).[1] However, the results of these studies have been conflicting.
Last updated: 5/11/2012

How might mannose-binding lectin protein (MBL) deficiency be treated?

Currently, there are no specific therapies available for mannose-binding lectin protein deficiency. Fresh frozen plasma may be used in emergencies to replace complement components. Routine vaccinations may be recommended (e.g., meningococcal vaccine, pneumococcal vaccine). Because a certain gene has been found to cause this condition, gene therapy may be a viable treatment in the future.[1]
Last updated: 4/9/2012

How can I learn about research involving mannose-binding lectin protein (MBL) deficiency? lists trials that are studying or have studied mannose-binding lectin protein (MBL) deficiency. Click on the link to go to to read descriptions of these studies.

You can also contact the Patient Recruitment and Public Liaison (PRPL) Office at the National Institutes of Health (NIH). We recommend calling the toll-free number listed below to speak with a specialist, who can help you determine if your wife is eligible for any clinical trials.  

Patient Recruitment and Public Liaison Office
NIH Clinical Center
Bethesda, Maryland 20892-2655
Toll-free: 1-800-411-1222
Fax: 301-480-9793
Web site:

You can find helpful general information on clinical trials at the following Web page.

Resources on many charitable or special-fare flights to research and treatment sites and low-cost hospitality accommodations for outpatients and family members, as well as ambulance services, are listed on the Web site of the Office of Rare Diseases (ORD), part of the National Institutes of Health.

Last updated: 1/9/2012