The impact of allogeneic hematopoietic stem cell transplantation on pulmonary complications in adults with inborn errors of immunity.

BACKGROUND Pulmonary involvement (repeated lung infections, lung parenchymal inflammation, scarring, and malignancies) is frequent in patients with inborn errors of immunity (IEI) and accounts for a significant proportion of the disease burden. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) can cure most severe IEI. The indications for allo-HSCT have recently been extended to adults. OBJECTIVE We sought to assess the impact of allo-HSCT specifically on respiratory status METHODS: We retrospectively analyzed data on 50 patients with IEI who underwent a first allo-HSCT after the age of 16 at three expert centers in France. RESULTS The median [interquartile range] length of follow-up was 4.8 years [IQR: 1.6;9.2] before allo-HSCT and 3 years [1.4;6.0] afterwards. Ten patients died from allo-HSCT-related complications. Four patients developed bronchiolitis obliterans syndrome. After the first-year post-transplantation, the mean annualized rate of severe respiratory infections (0.14 (95%CI: 0.04;0.24)) was lower than the value recorded before transplantation (0.54 (95%CI: 0.25;0.82); p=0.003 for paired comparisons of equivalent durations). Lung function was declining before allo-HSCT (mean (95%CI) FEV1: -2.09 %predicted/year (-7.27;3.09)] but increased afterwards (+2.44 %predicted/year (-4.79;9.69), p=0.0034 for paired comparisons). On CT scans of the chest, bronchial disorders and lung parenchyma cavities were the most frequent abnormal findings. The bronchial thickening and bronchiolar micronodules regressed after allo-HSCT, while bronchiectasis and residual parenchymal cavities were stable. CONCLUSION Allo-HSCT appears likely to protect the long-term pulmonary prognosis of adults with IEI; it is associated with a significantly lower incidence of severe respiratory infections, better lung function, and the radiological stabilization of lung damage.