Severe combined immunodeficiency (SCID) is a rare genetic disorder that is characterized by a lack of functioning immune system. It is caused by a genetic mutation that affects the development of several different types of white blood cells, which help the body fight off infection and disease. This mutation leads to a severe deficiency of the body’s ability to protect itself from foreign substances, leaving individuals with SCID highly susceptible to illnesses and infections.
The most common form of SCID is X-linked SCID. In this type, the faulty gene that causes the disorder is located on the X chromosome, which is passed down from the mother. Other types of SCID include autosomal recessive SCID, which is caused by the inheritance of two mutated genes, one from each parent, and adenosine deaminase deficiency (ADA)-SCID, which is caused by a genetic mutation in the ADA gene.
Individuals with SCID may experience recurrent and severe infections, often due to viruses, bacteria, or fungi. In addition, people with SCID are also prone to developing certain types of cancer, such as lymphoma. Without proper treatment, SCID can be fatal.
Treatment options for SCID include bone marrow transplants, gene therapy, and enzyme replacement therapy. Bone marrow transplants involve replacing the patient’s defective bone marrow with healthy, functioning bone marrow from a donor. Gene therapy is a newer form of treatment that involves replacing the defective gene with a healthy gene. Lastly, enzyme replacement therapy is used for individuals with ADA-SCID in order to replace the missing enzyme.
If left untreated, SCID can be fatal. With proper treatment, however, individuals with SCID can lead healthy, normal lives.