Abstract
Background: Transplantation of hematopoietic stem cells provide cure for severe combined immune deficiency (SCID) patients. Data on long-term outcome of this treatment in our area is limited. We report for the first time the long term survival after HSCT in SCID patients in Saudi Arabia. Methods: 108 transplants in 100 SCID patients have been performed between Jan 1993 to Dec 2006 at King Faisal Specialist Hospital, Riyadh, Saudi Arabia. 54% T-B- SCID. 13% T-B+ SCID, 13% ADA deficient SCID, 9% Omenn syndrome, 6% CD8 Lymphopenia, and 5% were unclassified with severe T cell dysfunction. Median age at HSCT was 7 months (range 1-77 months). The source of stem cell was mainly un-manipulated marrow from genoidentical or phenoidentical donor (93%), unrelated matched umbilical cord (4%) and peripheral stem cell from matched related donor (3%). 46% were not conditioned, 25% received Busulphan 16mg/kg and cyclophosphamide 200mg/ kg, 5% received additional ATG, 25% received cyclophosphamide only. GvHD prophylaxis consisted of cyclosporine (CSA) and methotrexate (MTX) in 35%, CSA alone in 45%, CSA and steroid in 3%, CSA and Mycophenolate Mofetil (MMF) in 2%, and no prophylaxis in 15%. Results: The overall survival at the time of analysis was 83% with reasonable engraftment as assessed by short tandem repeats for both lymphoid and myloid lineage. Patients with T-B+ had better prognosis than T-B-SCID (91% Vs 83% survival). On the other hand ADA deficiency had the worst outcome (71%). Transplant from HLA-genoidentical matched donor associated with the best outcome (89% survival). Patients received reduced intensity conditioning before stem cell transplantation had the most favorable outcome (95% survival), while non-conditioned patients had lower survival rate (83%). The worst prognosis as expected for patients received myeloablation (70% survival). However, among those who survived; patients received myelo-ablative chemotherapy had more stable engraftment with improved myeloid lineage and more stable immune reconstitution even for humoral immunity. Immune reconstitution and chimeric studies will be shown. Conclusion: Hematopoietic stem cell transplantation provides long-term cure and survival for SCID. Whenever available, genoidentical HLA matched donor is the best source for stem cells. Reduced intensity conditioning might be an option especially if it correlated with stable engraftment and long-term immune reconstitution. Further prospective long-term studies are required.