What Your Test Results Mean:

Carriers are not expected to show symptoms. You and your partner would both have to be carriers of ADA-related conditions for there to be an increased chance to have a child with symptoms; this is known as autosomal recessive inheritance. Carrier testing of your partner or donor is recommended in addition to consultation with a genetic counselor for a more detailed risk assessment.

Since this is an inherited gene change, this information may be helpful to share with family members as it may impact their family planning.

Disease Explained:

ADA-related conditions or adenosine deaminase (ADA) deficiency describes a group of metabolic conditions characterized by damage to the immune system. It is also a common cause of severe combined immunodeficiency (SCID). Reduced or eliminated activity of adenosine deaminase allows the buildup of deoxyadenosine to levels that are toxic to lymphocytes. Loss of these lymphocytes result in the signs and symptoms of SCID. As such, there are three different forms of adenosine deaminase (ADA) deficiency.

Adenosine Deaminase-Deficient Severe Combined Immunodeficiency Disease (SCID)

ADA-SCID is the most severe form of ADA-related conditions. The diagnosis of this form is often made within the first six months of life. Signs and symptoms can include recurrent pneumonia, severe diarrhea, and inflammation of the skin. Individuals may additionally experience growth failure, as well as neurological and skeletal abnormalities.

Delayed/Late-Onset Adenosine Deaminase Deficiency

Delayed or late-onset ADA is typically diagnosed between the ages of one and 10 years old. Rarely, a diagnosis may be made in the second or third decade of life. Symptoms are less severe than with ADA-SCID. Other symptoms can include but are not limited to common upper respiratory tract infections, ear infections, plantar and palmar warts, and allergies.

Partial Adenosine Deaminase Deficiency

Partial ADA is considered to be a benign condition that is consistent with normal immune response. Individuals with partial ADA typically only present with low levels of ADA enzymes in the blood.

Prognosis:

Prognosis depends on the severity of ADA diagnosed, how early treatment is started, and the response to treatment. With treatment and a successful hematopoietic stem cell transplant, individuals with ADA-SCID have about a 90% chance of survival for at least one year if the transplant is successful. Overall, the long-term outlook is considered to be generally good; however, without early diagnosis and treatment, babies with ADA deficiency usually do not survive past the age of two.

Treatment:

The primary form of treatment is a hematopoietic stem cell transplant (HSCT). If a transplant is not possible, enzyme replacement therapy can be considered. Gene therapy is still considered to be experimental in the United States.