Most children with SCID are treated with hematopoietic stem cell transplantation, or HSCT, also known as a bone marrow transplantation. HSCT is a challenging medical process that can take several months to complete. Most hospitals have a stem cell transplant patient coordinator who works with the family to guide them through the steps involved in HSCT.

In this treatment, hematopoietic stem cells are taken from a donor. The hematopoietic stem cells that are taken from the donor are infused into a child with SCID. Those cells multiply over time and develop an immune system for the child.

The reason these hematopoietic stem cells are used is because they are blood-forming cells. The hematopoietic stem cells produce red blood cells, white blood cells and platelets. White blood cells are the immune system cells comprised of neutrophils, T cells, B cells, and natural killer cells. White blood cells are the ones that provide people with a working immune system. Most of the white blood cells are lacking in a child with SCID, and an HSCT fixes that problem.