Pulmonary capillaritis as a manifestation of acute humoral allograft rejection following infant lung transplantation.

Pulmonary capillaritis has been described in adult lung transplant recipients, but has not been previously reported in pediatric recipients. We report a case of posttransplant pulmonary capillaritis in an 8-month-old infant, and demonstrate evidence of C4d deposition and B-lymphocytes in the allograft, donor anti-HLA antibodies in the serum and a clinical and immunohistochemical response to anti-CD20 monoclonal antibody (rituximab) therapy. These findings strongly support the hypothesis that pulmonary capillaritis may represent a form of acute humoral rejection in the lung allograft that is less common than, and clinically and histologically distinct from, typical acute cellular rejection.