Lumps: These are most likely cancerous. Take your mouse to the vet, and have it checked out. A checkup usually costs around 18 dollars.
Broken bones: If your mouse is limping around, and has a misplaced look to the bone, it is probably broken, it will heal on its own in a few weeks. Take out any tubes, ladders, or wheels preventing any further injuries to the bone.
Obesity: The simplest way to cure this is to put your mouse on a diet, and be sure they have ladders or wheels to exercise on. Give your mouse less seed mix, and pick out the sunflower seeds. Don’t feed it fatty foods like cheese, etc. Fawn colored mice(orange) are almost always obese. Wet Fur: Your mouse could be sweating. It could be too hot in the room, so turn on a fan, or turn the air cooler. Also, remove any cotton/flannel bedding that could be overheating them.
First Aid: The most important thing to do is give your mouse fluids to prevent dehydration, which can occur very quickly. A dropper or small syringe(no needle) will do the trick. Keep your mouse warm! Give it some flannel or cotton nesting materials. Injuries: Small wounds can be gently flushed with warm water and a MILD!! antiseptic, but if it is a major injury: Call the vet!
Abscesses: Since fighting is very common, the cuts that the mice get, can easily become infected. Clean them up with antibiotics. Respiratory Disease: The symptoms include : sneezing, red and watery eyes, and labored breathing. It can be caused by poor ventilation, strong scents, dirty cage bedding, or a dirty floor, where the ammonia from the urine is held.