i have a mouse and it has an unknown deasis

If your mouse is ill, it's best to take it to a veterinarian who knows about exotic pets. Write down as much information as you can such as when the mouse started showing symptoms of illness, what the symptoms are, the mouse's diet, how old the mouse is and how long you've had him, what type of cage, what bedding you use. All this will help the vet determine what is wrong with your mouse.