Five years after revealing she was diagnosed with the autoimmune disorder multiple sclerosis (MS), actress Christina Applegate has announced that she was misdiagnosed.

Speaking on Tuesday's episode of her MeSsy podcast, which she co-hosts with actress Jamie Lynn Sigler, Applegate said she wasn't happy to learn of the misdiagnosis, revealing that she has "gotten worse in some ways" and is "back at square one that I don't know what's going on with me." Doctors say there's no single test that can diagnose MS. That determination depends upon multiple factors, including a patient's symptoms and various test results, all of which can change over time.

Additionally, improper application of diagnostic criteria, and that fact that MS symptoms can resemble those of other conditions, can sometimes lead to misdiagnosis.