Adenosine Deaminase (ADA) Deficiency

What is Adenosine deaminase (ADA) deficiency?

Adenosine deaminase (ADA) deficiency is an inherited genetic disorder that causes damage to the immune system.  ADA deficiency leads to something known as severe combined immunodeficiency (SCID). Individuals with ADA deficiency and subsequent SCID lack almost all immune system protection from bacteria, viruses and fungi. These individuals are at risk of repeated, prolonged infections that can be life threatening.

It is estimated that ADA deficiency occurs in 1 in 200,000 to 1 in 1 million births.

What are the symptoms of ADA deficiency?

In most cases of ADA deficiency the symptoms appear before a child is 6 months of age. The symptoms are due to the body’s inability to fight off infection.  In many cases the infections experienced are caused by bacteria, virus or fungi a person without this disorder could fight off. Symptoms of ADA deficiency and the associated SCID include:

• Chronic diarrhea
• Pneumonia
• Skin rashes
• Absent tonsils and/or lymph nodes
• Slow physical growth
• Developmental delays

Some individuals with ADA deficiency develop symptoms later in life.  These cases can be seen between the ages of 1 and 10 years of age and occasionally early adulthood. The symptoms are essentially the same as the early onset individuals but tend to be less severe. Older patients with ADA deficiency may suffer from permanent lung damage, malnutrition and other chronic health concerns.

What causes ADA deficiency?

ADA deficiency is caused by a defect in the ADA gene.  This genetic defect interferes with the body’s production of a necessary enzyme known as Adenosine deaminase (ADA).  This enzyme is necessary for the proper breakdown and removal of a by-product of cell function known as Deoxyadenosine.  The buildup of this substance is toxic or harmful to the white blood cells of the body known as Lymphocytes.  These cells are necessary for the proper function of the body’s defense against infection. ADA deficiency must be inherited from the mother and the father.  A person with the genetic defect without the disorder is known as a carrier.

What are the available treatment options for ADA deficiency?

Treatment for ADA deficiency includes:

• Bone marrow transplant
• Injection of intravenous medications to boost immunity
• Early detection and treatment of infections
• Enzyme replacement therapy
• Gene therapy and stem cell therapy are of the newest treatments being researched

Where can I find more information about ADA deficiency?

• Genetic Home Reference: NIH
• NIH
• JRank