Objective
Allogeneic hematopoietic stem cell transplantation (HSCT) is the effective mean of immune restoration in severe combined immunodefiency (SCID). Whenever possible, HSCT without cytoreductive conditioning is attempted. Nevertheless, conditioning procedures are still preferred in a subset of patients. Herein we describe the immunological behavior in a cohort of conditioned and unconditioned patients.
Patients and Methods
This retrospective study was conducted on 17 SCID patients diagnosed before or on their admission, and later underwent HSCT. For the study`s purpose, they were divided into 2 groups: 10 who received conditioning, and 7 who did not. Immune reconstitution was assessed in the post-transplant year, by quantification of T-cell receptors excision circles (TRECs) and kappa-deleting recombination excision circles (KRECs), among additional laboratory and clinical evaluations.
Results
Unconditioned patients were diagnosed and transplanted earlier than conditioned ones. Serial TREC quantification showed a gradual increase in both groups, from undetectable levels towards normal values, with higher levels and significant change in the conditioned group. Sampled KREC results were also significantly higher in the conditioned group. Engraftment percentages differed drastically between groups, favoring the conditioned group. Unconditioned patients were significantly more dependent on IVIG than their counterparts. One patient from each group succumbed to disease complications.
Conclusion
Although pre-conditioning demonstrates superior laboratorial outcomes, waiving myeloablation should remain the treatment-of-choice in eligible patients, due to preferable morbidity. Patients with unique characteristics (i.e. consanguinity, BCG vaccination, impaired access to IVIG clinics) may require personalized considerations. The effort to implement secondary prevention of SCID with newborn screening should continue.
