'I was told to make plans for dying': Watch trailer for Selma Blair documentary

When Christina Applegate revealed earlier this week she had been diagnosed with multiple sclerosis, Selma Blair was right there to express her sympathy — because Blair has been struggling with her own MS diagnosis since 2018.

Now, Blair is the subject of "Introducing, Selma Blair," a discovery+ documentary focusing on how she's been coping and living with the disease. On Thursday, the platform tweeted a trailer for the forthcoming film, which will be released in both theaters and on streaming, calling it "a deeply intimate and powerful feature of @SelmaBlair in her journey of personal acceptance and resilience through her fight with Multiple Sclerosis."

In the trailer, Blair, 49, is shown dealing with the consequences of having her body rebel against her — she needs a cane, she walks unsteadily, she's exhausted easily, and she explains what it's like to not have enough air to say, "I can't breathe."

"I always thought I was on a reality show, like I was in a documentary, but only God would see it and disapprove," she says, as references to chemotherapy and stem cell transplants come up.

She adds later in the trailer, "I was told to make plans for dying. Not because I have MS, but because I'm fighting MS. ... I feel like I'm in the Tom Hanks movie ('Cast Away') where he's stranded on an island."

On Instagram, Blair shared the trailer and quipped, "Don't tell me how it ends."

Multiple sclerosis is an autoimmune disease in which the protective sheath that covers nerve fibers comes under attack. The disease can cause deterioration or permanent damage of the nerves, according to the Mayo Clinic.

The cause of MS remains unknown and there is no cure.

"I may be the subject of this film but my hope is that everyone sees themselves in it and finds some strength and joy they may not have known they had," the "Cruel Intentions" and "Anger Management" actor said in a news release earlier this year.

Some fans are already identifying strongly with what she's gone through: One person replied to the trailer tweet by writing, "This preview of this documentary is hard to watch especially if you suffer from MS. She is resilient and a(n) inspiration for everyone suffering from this horrible disease."

Another commenter noted, "My wife is battling MS and @SelmaBlair has been an inspiration to her."

"Introducing, Selma Blair" opens in theaters Oct. 15 and comes to the discovery+ streaming service Oct. 21.

Video: Selma Blair on low points of her 'quiet Christmas'