immunology allergic disorders
Severe Combined Immunodeficiency (SCID)
Treatment of SCID
Reverse isolation Supportive care using immune globulin replacement therapy, antibiotics, and antifungals Hematopoietic stem cell transplantation Enzyme replacement for ADA deficiency Gene therapy for ADA-deficient SCID Patients with severe combined immunodeficiency must be kept in reverse isolation. Treatment with Replacement of missing immune components replacement therapy, antibiotics (including In 90 to 100% of infants with SCID or its variants, Hematopoietic Stem Cell Transplantation from an HLA-identical, mixed leukocyte culture–matched sibling restores immunity. When an HLA-identical sibling is not available, haploidentical hematopoietic stem cells from a parent that is rigorously depleted of T cells can be used. If SCID is diagnosed by age 3 months, the survival rate after transplantation with either type of hematopoietic stem cells is 96%. Pretransplantation chemotherapy is unnecessary because patients do not have T cells and therefore cannot reject a graft. Patients with ADA deficiency who do not receive a stem cell transplant may be treated with injections ofpolyethylene glycol–modified bovine ADA once or twice a week. has been successful in ADA-deficient SCID, and no posttreatment leukemias or lymphomas have been reported. One publication showed highly favorable results of gene therapy in 50 ADA-SCID ( Treatment references ). Gene therapy has also been successful in X-linked SCID but has caused T-cell leukemias, precluding its use. Gene therapy for other forms of SCID is under study, including open enrollment in clinical trials for ADA-SCID and X-linked SCID. A small recent trial showed favorable results of gene therapy in Artemis-deficient SCID ( 1.Kohn DB, Booth C, Shaw KL, et al: Autologous ex vivo lentiviral gene therapy foradenosinedeaminase deficiency.N Engl J Med384(21):2002–2013, 2021. doi:10.1056/NEJMoa2027675 2.Cowan MJ, Yu J, Facchino J, et al: Lentiviral gene therapy for Artemis-deficient SCID.N Engl J Med387(25):2344–2355, 2022. doi:10.1056/NEJMoa2206575 