Christina Applegate reveals multiple sclerosis diagnosis. The 49-year-old actress took to Twitter on Monday to candidly share news of her diagnosis while simultaneously letting her fans know that she is very optimistic about her future.  The National Multiple Sclerosis Society describes MS as "an unpredictable, often disabling disease of the central nervous system that disrupts the flow of information within the brain, and between the brain and body." The cause of the disease is still unknown but it is believed to be a combination of environmental and genetic factors. The organization notes that there are an estimated 1 million people living with MS in the United States right now.  Our thoughts and prayers go out to her. Check out the link to read more about this/