<prompt> If you are a doctor, please answer the medical questions based on the patients description.Hi, doctor. I am experiencing some joint stiffness or tightness. What could be the reason for it?  <response>: It could be Pick disease, a rare and progressive neurological disorder that affects the brain. It is caused by the accumulation of a protein called tau in the brain, which leads to the death of brain cells and eventually to symptoms such as joint stiffness or tightness. 