A rare case of daratumumab-associated encephalopathy in multiple myeloma.

Daratumumab, a CD38 monoclonal antibody, has been widely used in patients with multiple myeloma. Although a variety of adverse events have been reported, consciousness impairment has not been reported yet. We report a case of encephalopathy associated with daratumumab. A 57-year-old male, diagnosed with relapsed multiple myeloma, was treated with daratumumab. He developed a loss of consciousness after the first administration. Cerebral spinal fluid and magnetic resonance imaging of the brain suggested encephalopathy. It is recommended to be aware of rare but life threatening side effects of daratumumab. We present a case of rare encephalopathy characterized by consciousness disorder associated with daratumumab, which was successfully resolved on prompt institution of steroids, although the mechanism was unknown.