It’s a disease called Idiopathic Environmental Intolerance Attributed to Electromagnetic Fields (IEI-EMF), more commonly known as Electromagnetic Hypersensitivity (EHS).

Unfortunately for sufferers of this disease, it doesn’t seem to exist. People who believe themselves to have EHS report a wide range of symptoms that they believe are caused by exposure to radio, Wi-Fi, and other electromagnetic waves. Some even move to remote towns for relief. But studies have shown again and again that a link between electromagnetism and the symptoms is nonexistent (hence the “attributed” in the disease name).

Chuck McGill is the victim of a neuropsychological disorder similar to Morgellons. It’s unclear whether Jimmy McGill believes his brother’s disease is real or not. But Saul does seem to understand that the likelihood of Chuck McGill beating his disease is very slim.