A case of autoimmune encephalitis with involuntary movements as the first symptom and suspected association with mumps virus infection.

This case involved a 72-year-old woman. From the day after mitral annuloplasty, a fever over 37°C and ballismus-like involuntary movements of the right upper and lower limbs appeared. A few month later, involuntary movements spread throughout the body, and she developed impairment of consciousness and difficulty speaking and eating. Levels of protein in cerebrospinal fluid were high. Positive results were seen for serum mumps immunoglobulin G and M antibody. Because steroid pulse therapy proved effective, we suspected autoimmune encephalitis associated with mumps virus infection.