A U.S. film about a rare but serious disease that impairs the body's autoimmune system is being shown in Japan, boosting hope among patients and their families that it will help raise awareness of the little-known illness.

"Brain on Fire," released in Japan on Dec. 16, is based on a 2012 memoir of the same name by journalist Susannah Cahalan, who in 2009 came down with the disease, called anti-NMDA receptor encephalitis.

The book vividly depicts how Cahalan, then a 24-year-old budding reporter at the New York Post, started experiencing fatigue, numbness, insomnia and memory loss. Her condition worsened in the following weeks as she started exhibiting violent and psychotic behavior and suffered from seizures.