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With adenosine deaminase severe combined immune deficiency
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Patients with ADA-SCID who are left untreated often die of infection by 2 years of age
ADA-SCID is an ultra-rare, inherited genetic disorder caused by a deficiency in the ADA enzyme responsible for purine metabolism. Mutations in the ADA-SCID gene result in a lack or dysfunction of ADA. SCID is characterized by the absence of functional T cells, lack of proper B-function, and reduced number of NK cells. ADA-SCID is fatal in infancy without treatment intervention. This is often due to multiple severe infections, severe chronic diarrhea, and failure to thrive.
Most patients develop symptoms of ADA-SCID before 6 months of age. It is typically diagnosed with newborn screening but may also be confirmed by blood and genetic test results.
The earlier ADA-SCID is detected, and treatment initiated, the better the outcome.
Chiesi Global Rare Diseases is a sponsor of the Jeffrey Modell Foundation genetic testing program as a part of their commitment to early diagnosis of primary immunodeficiency.
For more information, or to refer to an expert immunologist within the Jeffrey Modell Centers Network, click learn more.
There are two FDA-approved treatment options for ADA-SCID in the US. Other potential approaches are investigational and have not been approved by the FDA.
ADA deficiency is caused by mutations in the gene responsible for making the ADA enzyme
1. In healthy cells, the function of the ADA enzyme is to convert harmful deoxyadenosine (dAXP) to a
2. Mutations in the ADA gene lead to a non-working, or poorly working ADA enzyme, resulting in reduced or eliminated ADA activity.
3. The absence of ADA leads to dAXP build up within the lymphocytes, compromising the immune system.
4. Due to this build-up, the risk of severe and recurring infections increases.
ADA-SCID can present with early onset or delayed/late onset symptoms.
- Deficiencies in humeral and cellular immune function
- Low serum immunoglobulins
- Lack of lymphoid tissue
- Failure to thrive
- Opportunistic infections
- Infections: recurrent otitis, sinusitis, and upper respiratory infections
- As the disease progresses: chronic pulmonary insufficiency, cytopenia, antithyroid antibodies, allergies, and elevated serum immunoglobulin (IgE)
Some patients with ADA-SCID may show reduced neutrophil counts and bone marrow abnormalities, including myeloid dysplasia and hypocellularity.
Early detection = early initiation of treatment
Newborn screening allows for timely detection of ADA-SCID. Diagnosis may also be confirmed
by measuring ADA erythrocyte activity and/or genetic testing. The earlier ADA-SCID can be detected,
and treatment started, the better the outcome.
Learn more about ADA-SCID diagnosis and treatment.
ADA-SCID diagnosis may be confirmed with a:
A blood test that measures ADA enzyme activity
Genetic testing for an ADA gene variation
Genetic testing can also be used to confirm a diagnosis via a blood test.
How ADA-SCID is inherited
Carriers typically do not show signs or symptoms of the condition.
Two carriers, each with 1 gene variant, have a:
chance of having a child unaffected by
chance of having a child who has 1 defective ADA gene but is not affected by
chance of having a child with 2 defective ADA genes who may be affected by
Genetic testing can be used to confirm a diagnosis when a primary immunodeficiency (PI) like ADA-SCID is suspected.
For more information, or to refer to an expert immunologist within the Jeffrey Modell Foundation Centers Network, please click on learn more.
There are potential approaches that are investigational
and have not been approved by the FDA.