Adenosine deaminase (ADA) deficiency is a disorder that affects the immune system. Specifically, ADA deficiency impairs the development and function of immune cells called lymphocytes. Lymphocytes are white blood cells that help the body fight infections. As a result, people with ADA deficiency often develop pneumonia, chronic diarrhea, and widespread skin rashes. Additional signs and symptoms of ADA deficiency include slow growth and developmental delays.

Adenosine deaminase deficiency is caused by variants (also called mutations) in the ADA gene. This gene provides instructions for producing the enzyme adenosine deaminase. This enzyme is found throughout the body but is most active in lymphocytes. These cells protect the body against foreign invaders, such as bacteria and viruses. Lymphocytes are produced in specialized lymphoid tissues throughout the body, including in a gland located behind the breastbone called the thymus and in the lymph nodes.

Adenosine deaminase deficiency is very rare. It is estimated to occur in approximately 1 in 500,000  newborns worldwide. Approximately 15 percent of people with SCID have ADA deficiency.

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell must have a variant to cause the disorder. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Published Date: May 21, 2024
Published By: National Institutes of Health