Darnay's disease

From Memory Alpha, the free Star Trek reference

Darnay's disease is an terminal disease with no known cure which attacks the central nervous system and the brain. Among its symptoms are coughing, pain, shortness of breath, irritability, and erratic behavior.

In 2365, Doctor Ira Graves was diagnosed with the final stages of Darnay's disease. (TNG: "The Schizoid Man")