SCID includes genetic diseases that are both rare (about 1 case per 60,000 births) and serious: these diseases are characterized by “a profound deficit in cellular (linked to T lymphocytes) and humoral (linked to antibodies) immunity , resulting in infants with a high predisposition to serious infections “which can lead to their death, specifies the High Authority for Health (HAS).
She recommends to reduce diagnostic error and give these children a chance – without treatment, most of them die of infections before their first birthday – a screening test just after birth.
T cell count
But how ? Thanks to a quantification test of TRECs (T-cell receptor excision circles) from a drop of blood dried on blotting paper (the famous Guthrie test). This count makes it possible to measure a possible deficit in T lymphocytes, which can put on the track of the DICS. If the diagnosis is confirmed, a genetic study is carried out in order to identify the type of molecular abnormality.
Then the treatment is put in place: it consists of transplanting hematopoietic stem cells (which produce blood cells) in order to replace the failing immune system of the children, and thus cure them. The sooner this transplant is performed after birth, the greater its effectiveness, recalls the HAS.
“The optimal time frame (…) is to be able to transplant the child before two months of life if we want to prevent the risk of the occurrence of serious infections, in particular those caused by cytomegalovirus”, viruses related to the viruses of herpes that cause chickenpox and mononucleosis.