Severe combined immunodeficiencies (SCID) are rare genetic disorders causing immune failure, leading to recurrent, life-threatening infections. Allogeneic hematopoietic stem cell transplantation (HSCT) is the most effective treatment.
To assess bone marrow transplantation outcomes in children with SCID.
A retrospective study in the pediatric immunohematology and HSCT unit of the National Bone Marrow Transplant Centre, Tunis, over 18 years (2007–2024). It included patients with SCID who underwent HSCT. Conditioning regimens and complications were defined per 2019 EBMT criteria.
Among 28 patients (14 boys, 14 girls), immunophenotypes were: T-B-NK+ (n = 19), TB+NK+ (n = 7), T-B+NK- (n = 1), and T-B-NK- (n = 1). The median age at diagnosis was 4 months (Q1 = 1, Q3 = 5), and at HSCT, 7 months (Q1 = 3, Q3 = 8). Sixteen had pretransplant infections, including BCGitis (n = 10), CMV (n = 3), RSV (n = 3), and invasive aspergillosis (n = 2). Transplants were genoidentical (n = 8) or haploidentical (n = 20). Conditioning regimen included Busulfan-Fludarabine (n = 17) or Treosulfan-Fludarabine (n = 9), with serotherapy in haploidentical cases (n = 20); two patients had no conditioning. Engraftment occurred in 27 of 28 patients. Mean neutrophil and platelet recovery times were 22 ± 12 days (range: 14–47) and 24.5 ± 12.8 days (range: 7–45), respectively. One child had primary graft failure. Post-transplant complications included acute GvHD (n = 10), hepatic veno-occlusive disease (VOD) (n = 13), viral infections (n = 13; CMV reactivation = 8; viral co-infections = 5), thrombotic microangiopathy (n = 3), BCG reactivation (n = 4), and autoimmune cytopenias (n = 2). After a median follow-up of 2.5 years (Q1 = 1, Q3 = 5), the 5-year survival probability was 65%. Nine early deaths were due to VOD (n = 4), disseminated viral infection (n = 3), thrombotic microangiopathy (n = 1), and septic shock (n = 1).
HSCT outcomes for SCID depend on pretransplant conditions, but toxic and infectious complications remain a challenge. Early diagnosis and avoiding live vaccines are crucial.
