Alemtuzumab is a monoclonal antibody approved for relapsing-remitting multiple sclerosis (RRMS). The only report of Serum Sickness (SS) in a MS patient occurred during treatment with natalizumab. Non-protein drugs, such as some antibiotics, may induce "SS-like" reactions (SSLR), whose clinical and laboratory features may partially overlap with the traditional SS.
To report a case of SS/SSLR in a RRMS patient treated with alemtuzumab.
A 42-year-old-woman with RRMS developed SS/SSLR in the first week after the first alemtuzumab treatment. Concomitant medications included trimethoprim-sulfamethoxazole at low dose. Intravenous methylprednisolone therapy led to clinical resolution and normalization of serum inflammatory markers.
SS/SSLR should be considered in patients treated with alemtuzumab developing delayed fever, rash and arthralgia and differentiated with Infusion Associated Reactions (IARs) and infections.