A case of late-onset neutropenia secondary to rituximab in a patient with mucous membrane pemphigoid

Rituximab (RTX) is increasingly used in the treatment of autoimmune blistering disorders (AIBDs). Neutropenia associated with RTX has been reported in the treatment of hematologic and rheumatic conditions,1, 2 occurring both shortly after treatment and weeks to months later. Definitions of early-onset neutropenia (EON) and late-onset neutropenia (LON) have been variable in the literature (Table I), with presentation ranging from an asymptomatic laboratory test value to critical illness. Few cases of RTX-associated neutropenia in the setting of AIBDs have been reported.3, 4, 5, 6 Here, we present a case of LON secondary to RTX occurring in a patient with mucous membrane pemphigoid (MMP), a condition in which RTX-associated neutropenia has not been reported to our knowledge. Table I Neutropenia definitions