Researchers at UCSF and Chan Zuckerberg Biohub have discovered a novel biomarker for an autoimmune disease that affects patients with testicular cancer. The disease, known as “testicular cancer-associated paraneoplastic encephalitis,” can cause severe neurological symptoms. The symptoms include loss of limb control, eye movement, and in some cases, speech. The disease begins with testicular cancer, which in some cases causes the immune system to attack the brain. Affected patients are often misdiagnosed and appropriate treatment is delayed.