Causes of MBL deficiency

Genetic changes (known as mutations) in the MBL2 gene can lead to MBL deficiency. This gene provides instructions for making the MBL protein that plays an important role in the body’s immune response. MBL protein attaches to foreign invaders such as bacteria, viruses or yeast and turns on (activates) another important part of the immune system known as the complement system.

Variants in the MBL2 gene reduce the production of the MBL protein, so sometimes MBL deficiency may be referred to as MBL protein deficiency. The reduction of MBL in the blood means that the body does not recognise and fight
foreign invaders (e.g. bacteria, viruses or yeast) efficiently. That is why infections
can be more common in people with this condition.

Family planning and MBL deficiency

The inheritance pattern of MBL deficiency is not fully understood. People may inherit an increased risk of developing MBL deficiency but not develop symptoms of the condition. Furthermore, not everyone with a change in the MBL2 gene has decreased levels of MBL, and not everyone with decreased protein levels is prone to infection. For these reasons it is more usual to measure the protein level in the blood than undertake genetic studies. Researchers believe that a number of factors, including other genetic and environmental factors, are involved in the development of MBL deficiency.