In 2005, I finally got an MS diagnosis. It began in my left hand with tingling, numbness and weakness that traveled up my left arm, the same arm I broke when I fell in 1995. I underwent a series of tests for multiple sclerosis over the next four months. (For more information on criteria and testing, read "Beginner's Guide to MS: Do I have MS? What does it take to get diagnosed with MS?")

The MS diagnosis was not a surprise to me since it had been a possibility after having optic neuritis in 2000. However, the RA diagnosis was a surprise at the time and friends asked, "Does this mean that you do not have MS?" My quick response was, "No, it just means that I double-dipped in the autoimmune disease bucket."

Day to day, overlapping symptoms (such as fatigue, weakness, numbness, and brainfog) can create a challenge in guessing which disease is the culprit. Some days it doesn't matter the cause of the symptom, the treatment is the same. Rest.

With more than 80 types of autoimmune diseases, no wonder it is difficult to diagnose one, much less two or more in one person. (See MedLinePlus article)

If you are someone living with rheumatoid arthritis and worried that you are developing multiple sclerosis, or if you have developed multiple sclerosis, please know that it is not the end of the world. Your choices for RA treatments are limited, but RA doesn't affect how MS is treated. If you have more questions about MS and RA, I'm glad to try to answer them.

Lisa Emrich is author of the blog Brass and Ivory: Life with MS and RA and founder of the Carnival of MS Bloggers.