Complement component 2 deficiency is a disorder that causes the immune system to malfunction, resulting in a form of immunodeficiency. Immunodeficiencies are conditions in which the immune system is not able to protect the body effectively from foreign invaders such as bacteria and viruses. People with complement component 2 deficiency have a significantly increased risk of recurrent bacterial infections, specifically of the lungs (pneumonia), the membrane covering the brain and spinal cord (meningitis), and the blood (sepsis), which may be life-threatening. These infections most commonly occur in infancy and childhood and become less frequent in adolescence and adulthood.

Complement component 2 deficiency is caused by mutations in the C2 gene. This gene provides instructions for making the complement component 2 protein, which helps regulate a part of the body's immune response known as the complement system. The complement system is a group of proteins that work together to destroy foreign invaders, trigger inflammation, and remove debris from cells and tissues. The complement component 2 protein is involved in the pathway that turns on (activates) the complement system when foreign invaders, such as bacteria, are detected.

In Western countries, complement component 2 deficiency is estimated to affect 1 in 20,000 individuals; its prevalence in other areas of the world is unknown.

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.

Published Date: June 01, 2014
Published By: National Institutes of Health