Author response: Rare side effects of alemtuzumab remind us of the need for postmarketing surveillance.

Abstract

We thank Drs. Whiteside and Trip for their comment on our editorial.1 The authors highlight noninfectious pneumonitis as a rare potential complication of alemtuzumab.2,3 The time course of onset in the 2 reported cases was different, with symptoms developing a few days or 1 month after infusion. Although not proven, this suggestion of immune-mediated mechanisms seem reasonable.2 This reaction may arise from antibody-dependent cell-mediated or complement-mediated cytolysis, which leads to cytokine release and then type III/IV hypersensitivity reaction and lung-resident T-cell activation. As for the side effects highlighted in our editorial,1 clinicians should recognize noninfectious pneumonitis as a potential rare complication of alemtuzumab, as it can respond well to corticosteroids.