Severe pneumonia with formation of a pulmonary cavity associated with long-term rituximab therapy in multiple sclerosis.

Nowadays B-cell depletion via anti-CD20 antibodies is commonly applied in the treatment of multiple sclerosis (MS). Yet, not much is known about infection risks associated with long-term B-cell depletion in the specific context of MS. We present the case of a 45-year-old male patient who developed severe pneumonia following 6 years of rituximab treatment for highly active relapsing-remitting MS. The patient had no additional chronic disease as well as no history of foreign travel. Although the unusual formation of a pulmonary cavity raised suspicion for tuberculosis, repeated testing via bronchoscopy and sputum remained negative. Prolonged antibiotic therapy with piperacillin/tazobactam and amoxicillin/ clavulanate led to complete recovery from symptoms. This case shows the potential risk of serious infections following continuous B-cell depletion in MS and illustrates the importance of future vigilance.