Abstract

A 55-year-old lady with 3 years history of relapsing remitting multiple sclerosis (MS) developed primary central nervous system lymphoma (PCNL) after receiving only three doses of natalizumab monotherapy. The diagnosis was confirmed by brain biopsy. There are three reported patients with MS who developed PCNL while on natalizumab treatment. Because there is no increased prevalence of PCNL in MS and with the increase use of biological agents, this case highlights the importance of clinical vigilance and awareness of rare complications.