Severe combined immunodeficiency (SCID) is a heterogeneous group of lethal congenital disorders which result in the absence of antigen-specific T and B lymphocyte responses. It is estimated to occur in 1/50,000 – 100,000 live births. Most children with SCID present about 3-8 months of age with failure to thrive, persistent diarrhea, severe bacterial, viral and/or fungal infections or pneumonia. Babies with SCID will usually die from infections within a year.
There are many different types of SCID.
A blood or marrow transplant is the only known cure for SCID, although the use of gene therapy to correct these diseases is being explored. For some infants with SCID who have a genotypically HLA matched sibling donor, pre-transplant chemotherapy is not needed to achieve engraftment. However, those with some other forms of SCID and those without a matched sibling donor utilizing an unrelated donor or umbilical cord blood unit, require some chemotherapy prior to transplant. The purpose of the transplant is to replace the defective T and B lymphocytes and provide the patient with a functioning immune system.
It is recommended that patients with SCID be referred to a transplant center as soon as they are diagnosed within the first few months of life.