it. First up in the heat index. Actress Kristen Johnson talking to "People" magazine about a rat wl a rare disease. Paula Faris has her story. Reporter: From an out of this world funny alien on "Third... See More
it. First up in the heat index. Actress Kristen Johnson talking to "People" magazine about a rat wl a rare disease. Paula Faris has her story. Reporter: From an out of this world funny alien on "Third rock from the sun." Women are trouble. I should know. I've been one for two weeks. Reporter: To a single and sometimes desperate divorce attorney. I'll have the shrimp cocktail. Reporter: She's played it all. Now the 46-year-old actress is opening up to "People" magazine about the rare form of Lupu sx that turned her world into a real-life me call mystery. It was like swimming through Mo lasses. Reporter: She said she new something was Yong last summer when she had trouble climbing a flight of stairs. I couldn't walk. It was incredible. Reporter: After four months, a battery of tests, and 17 different doctors, Johnston was finally diagnosed with lupus sms myelitis. A neuroroj call disorder that attacks the spine. When I finally found out what it was, I had treatment. And started feeling a little better. Doctors say if she waited a few more weeks to seek treatment, she could have ended up a quadriplegic. Reporter: It's the latest perm battle for her who came clean about her struggle with alcohol and pain kills in 012. Stlst so much secrecy. I think it keeps people sick. I do. Reporter: Still sober and now in remission, Johnston is back at work. And thankful to be alive. Yes, yes, yes. It was such a life-changing experience, this five-month journey I went on. Reporter: For "Good morning America," Paula Faris, ABC news, New York.
This transcript has been automatically generated and may not be 100% accurate.