Restitutio ad integrum: Rescuing the Alveolar Macrophage Function with HSCT in Pulmonary Alveolar Proteinosis Due to CSF2Rα Deficiency.

Hereditary pulmonary alveolar proteinosis (hPAP) is a rare lung-related primary immunodeficiency. In hPAP, variants of genes encoding the heterodimeric GM-CSF receptor alpha or beta-chains (CSF2Rα, CSF2Rβ) lead to perturbations in GM-CSF signalling. These perturbations impair the scavenging function of pulmonary alveolar macrophages leading to accumulation of surfactant proteins and lipids within the alveoli. The replacement of defective pulmonary alveolar macrophages can be achieved with allogeneic hematopoietic stem cell transplantation. However, previous reports highlight undesirable pulmonary outcomes associated with this therapeutic approach. We report a 4-year-old developmentally normal girl born of second-degree consanguineous marriage diagnosed with severe form of CSFRα-deficient PAP. She required recurrent whole lung lavage and hence was treated with allogeneic hematopoietic stem cell transplantation. A reduced toxicity treosulfan-based myeloablative regimen with alemtuzumab serotherapy was used for conditioning. Ciclosporin, mycophenolate mofetil and FAM (fluticasone inhaler, azithromycin, montelukast) were used to prevent graft-versus-host disease and immune-related complications of lung. Her post-transplant course was uneventful with full donor chimerism and complete resolution of symptoms. We demonstrate for the first time in a case of severe CSF2Rα-deficient PAP, the successful use of hematopoietic stem cell transplantation as a primary curative treatment, restoring normal lungs both anatomically and functionally. The case report provides evidence for considering allogeneic hematopoietic stem cell transplant in severe forms of CSF2R-deficient PAP.