Having a pet is a rewarding experience, probably one of the most rewarding things that you will ever do in your life. Some people are dedicated dog people and other people prefer cats. Every once in awhile, you run into someone that likes to have both types of animals around at the same time. If you are going to have cats in your life, you should plan on having them for about 15 years, as this is the common lifespan for most cats. With that being said, there are a lot of diseases that routinely affect cats. Some of them are relatively minor and might resolve on their own while others are far more serious and require immediate veterinary care. Below you will find a list of 20 of the most common diseases in cats, along with some important information about each one.