Risk factors of rituximab-induced thrombocytopenia in patients with autoimmune bullous diseases.

Rituximab has been the mainstay treatment for autoimmune bullous diseases (AIBDs). Among the side effects of rituximab, rituximab-induced thrombocytopenia (RIT) is a rare but critical complication. However, there have been no reports or identification of risk factors for RIT in patients with AIBD. In our retrospective study, we compared rituximab-treated AIBD in patients with and without thrombocytopenia to explore the risk factors. In addition, we compared two different rituximab protocols (rheumatoid arthritis [RA] and lymphoma) in terms of the incidence and severity of thrombocytopenia. A total of 222 patients were enrolled, and 46 patients (20.7%) developed RIT. Multivariate logistic regression analysis identified age and chronic kidney disease (CKD) as significant factors for RIT. We also found that patients treated with the lymphoma protocol demonstrated a significantly higher mean post-rituximab platelet count compared with those on the RA protocol. This was the first analysis, to our knowledge, of risk factors for RIT in patients with AIBD. Individuals aged 70 or older and those with multiple comorbidities, particularly CKD, should be closely monitored for thrombocytopenia. For patients with CKD, it may be safer to use the lymphoma protocol for rituximab administration as it results in a lesser reduction in post-rituximab platelet count.