Rituximab-induced serum sickness is more frequent in autoimmune diseases as compared to hematological malignancies: A French nationwide study.

INTRODUCTION

Rituximab induced serum sickness (RISS) is a rare delayed hypersensitivity reaction. The aim of this study was to describe the epidemiological and clinical characteristics of the RISS cases reported in France.

METHOD

Serum sickness cases involving rituximab were identified from the French PharmacoVigilance Database from 1998 to 2016.

RESULTS

We analyzed 37 cases of RISS. Rituximab was prescribed for an autoimmune disease in 78% of cases. Serum sickness occurred mainly after the first injection (54%) with a median time to onset of 12 days. The most frequent manifestations were rheumatologic symptoms (92%), fever (87%), and skin lesions (78%). The incidence was significantly higher when rituximab was used for autoimmune diseases than for a hematological malignancies. Taking into account the existence of a Systemic Lupus Erythematosus (SLE) as the indication of rituximab or as a comorbidity, the incidence of RISS in patients with SLE was even higher.

DISCUSSION

We report on the largest series of RISS studied to date and confirm that this reaction preferentially occurs in patients with autoimmune disease, especially SLE. This may be due to B-cell lysis, leading to the release of intracellular antigens into the serum and subsequent antigen-antibody complex formation, especially in patients with elevated autoantibody production. This could also explain why RISS often occurred after a single injection.

CONCLUSION

Patients generally recovered from RISS rapidly without obvious benefit from corticosteroid therapy. The risk of recurrence should prompt clinicians to question the use of rituximab after an episode of RISS.