After a child with SCID is under a specialist’s care, the next step in the HSCT process is to run tests to make sure that the child is healthy enough to undergo the transplantation. The child might have blood tests, CT scans, and ultrasounds. Doctors also test the child’s kidneys, heart, lungs, and other organs.
If the child is healthy enough for the transplant, then the child will receive a temporary IV line in a vein in the chest. This line is called a central line. The child will go under general anesthesia in order for the central line to be put in. The central line helps the doctors take blood from the child on a daily basis so that they can monitor progress of the immune system. Doctors also use the line to administer antibiotic, antiviral, and antifungal medications to prevent infections from developing.
Another type of treatment that the child will receive through the central line is immunoglobulin replacement therapy, or Ig. Ig is prepared from human plasma. Human plasma is a yellowish liquid that is part of a person’s blood and can be separated out from the blood during a procedure called plasmapheresis. The plasma contains proteins and antibodies that are very important in keeping the child with SCID healthy. The Ig that is made from plasma contains antibodies that will help a child with SCID prevent and fight against infection. The centers that collect the plasma send it to facilities for purification so people with immune deficiencies can use it.
Before a child undergoes the transplant, he or she may receive conditioning.
Conditioning means the doctor will give the patient chemotherapy and/or other immune suppressing drugs to kill the bone marrow cells of the patient and weaken what remains of the child’s immune system.
The reason doctors weaken the child’s immune system is because they want the new donor immune system cells to take over and not be stopped by the child’s. The reason doctors kill the bone marrow cells in the child is to give the donor cell a place to grow. This is also called “making room” for the new cells.
Sometimes doctors treat the child with only chemotherapy, sometimes with chemotherapy and immune suppressing drugs, and sometimes with just immune suppressing drugs.
The drugs are administered intravenously in the days before the HSCT.