Shortly after Knut suffered a seizure and collapsed into a pool in his enclosure at the Berlin Zoo, the autopsy results were announced: Knut's seizure was triggered by swelling in his brain and he most likely died by drowning after falling unconscious in the water. But scientists have continued to study the bear, in part hoping to learn more about how to save others if similar situations arise, and in part because no pathogen could be found to explain the swelling.
Dr. Harald Prüß, at the German Center for Neurodegenerative Diseases (DZNE), thought Knut's symptoms looked a lot like those of his patients. The neurology specialist teamed up with Prof. Alex Greenwood, at the Leibniz Institute for Zoo and Wildlife Research (IZW), . Together, they have proven that Knut was the victim of an autoimmune disease.
Knut is the first animal, wild or domesticated, ever to be diagnosed with "anti-NMDA receptor encephalitis," a non-infectious form of encephalitis in which the body's own immune system attacks the brain, damaging nerve cells and causing symptoms that start with headaches and nausea but progress to hallucinations, seizures, and more severe consequences. Now that the disease has been documented, other cases of encephalitis without a clear cause may be similarly diagnosed in animals.
Perhaps this will help scientists to better understand anti-NMDA receptor encephalitis, which can be treated with drugs. According to Prüß: “We might underdiagnose autoimmune inflammations in human patients suffering psychoses or memory disturbances, because these patients are not routinely screened for associated antibodies. As a result they may not receive the optimal treatment." If Knut's death helps heal people and other animals, it would further add to the legacy of one very special polar bear.