Hematopoietic stem cell transplantation for CD40 ligand deficiency: results from an EBMT/ESID-IEWP-SCETIDE-PIDTC Study

BACKGROUND: CD40 ligand (CD40L) deficiency, an X-linked primary immunodeficiency, causes recurrent sinopulmonary, Pneumocystis and Cryptosporidium infections. Long-term survival with supportive therapy is poor. Currently, the only curative treatment is hematopoietic stem cell transplantation (HSCT). OBJECTIVE: We performed an international collaborative study to improve patients' management, aiming to individualize risk factors and determine optimal HSCT characteristics. METHODS: We retrospectively collected data on 130 patients who underwent HSCT for CD40L deficiency between 1993-2015. We analyzed outcome and variables relevance with respect to survival and cure. RESULTS: Overall survival (OS), event-free survival (EFS) and disease-free survival (DFS) were 78.2%, 58.1% and 72.3% 5 years post-HSCT. Results were better in transplants performed ≥2000 and in children <10 years old at HSCT. Pre-existing organ damage negatively influenced outcome. Sclerosing cholangitis was the most important risk factor. After 2000, superior OS was achieved with matched donors. Use of myeloablative regimens and HSCT ≤2 years from diagnosis associated with higher OS and DFS. EFS was best with matched sibling donors, myeloablative conditioning (MAC) and bone marrow-derived stem cells. Most rejections occurred after reduced intensity or non-myeloablative conditioning, which associated with poor donor cell engraftment. Mortality occurred mainly early after HSCT, predominantly from infections. Among survivors who ceased immunoglobulin replacement, T-lymphocyte chimerism was ≥50% donor in 85.2%. CONCLUSION: HSCT is curative in CD40L deficiency, with improved outcome if performed before organ damage development. MAC is associated with better OS, EFS and DFS. Prospective studies are required to compare risks of HSCT with those of life-long supportive therapy