Mannose-binding lectin deficiency
Mannose-binding lectin deficiency is an immune system condition characterized by low levels of a specific blood protein, which may increase susceptibility to certain infections.
Overview
Mannose-binding lectin deficiency is a condition that affects the immune system. People with this condition have low levels (deficiency) of an immune system protein called mannose-binding lectin in their blood. Whether this deficiency makes affected individuals prone to recurrent infections is not clear.
Symptoms
People with this condition can develop infections of the upper respiratory tract and other body systems. Individuals may also contract more serious infections such as pneumonia and meningitis. Symptoms vary in frequency and severity depending on the type of infection.
- Infants and young children appear more susceptible to infections than adults.
- Adults can also develop recurrent infections.
- Individuals undergoing chemotherapy or taking drugs that suppress the immune system are especially prone to infections.
Causes & Risk Factors
The condition is linked to mutations in the MBL2 gene. This gene provides instructions for making a protein that assembles into a complex called mannose-binding lectin.
- Immune Function: Mannose-binding lectin attaches to foreign invaders like bacteria, viruses, or yeast to activate the complement system, a group of proteins that destroy pathogens and trigger inflammation.
- Mutation Impact: Mutations in the MBL2 gene can reduce the production of the protein or prevent it from assembling into a functional complex.
- Variability: Not everyone with an MBL2 gene mutation has decreased protein levels, and not everyone with low levels is prone to infection. Researchers believe other genetic and environmental factors are involved.
Frequency
This deficiency is thought to affect approximately 5 to 10 percent of people worldwide. Many affected individuals show no signs or symptoms. The condition is more common in certain populations, such as sub-Saharan Africans.
Inheritance
The inheritance pattern is unclear. Some reports suggest that a mutation in one copy of the MBL2 gene in each cell can lead to the condition, while others suggest a mutation in both copies is necessary. People inherit an increased risk of developing the deficiency, not the condition itself; not all people who inherit these mutations will develop the condition.