What is SCID ADA?
Severe combined immunodeficiency (SCID) refers to a group of immunodeficiency disorders caused by various genetic defects. SCID ADA represents approximately 10-15% of all SCID and is due to adenosine deaminase (ADA) deficiency; ADA is required for the degradation of deoxyadenosine after DNA breakdown. Its main defect leads to abnormal lymphocyte production and function. The incidence of SCID ADA is estimated at 1:1,000,000 newborns.
SCID ADA patient presents with a decreased serum level of both T and B lymphocytes, key actors of the immune system. Consequently, severe and repeated infections (bacterial, viral and mycotic) occur in these patients.
What are the symptoms of SCID ADA?
In most patients, severe infections start as early as within the first months of life (early onset form). Some infants may die of overwhelming sepsis before the diagnosis is made. If untreated, patients are generally not expected to live beyond the age of one year. Less frequently, symptoms can develop later, within the first years of life with repeated infections and retarded growth. This non-specific presentation can delay the diagnosis. Blood analysis shows a low level of lymphocytes and immunoglobulins.
How is SCID ADA diagnosed?
The diagnosis is made by measuring the activity of ADA in red blood cells.
How is SCID ADA treated?
Early diagnosis and treatment of SCID ADA is crucial. Possible therapeutic approaches include bone marrow transplantation and enzyme replacement therapy (PEG-ADA). Bone marrow transplantation is the treatment of choice if a matched family donor is available and if the patient presents with an early onset disease. Alternatively, the option of enzyme replacement therapy consists of regular injections of the deficient enzyme as a life long treatment. So far, about 150 SCID-ADA patients have been treated with PEG-ADA over the last 20 years. |
