Christina Applegate shared the heartbreaking news that her daughter Sadie has been diagnosed with POTS.

The Vacation starlet's 13-year-old daughter spoke out about her circumstances during the talk at her mother's MeSsy podcast, admitting that she now has an experience with her mother, who has been managing multiple sclerosis.

Sadie shared, “I have something called POTS.”

She continued, “I have no clue what it actually is, but it’s something to do with the autonomic nervous system and it affects my heart. When I stand up, I get really, really dizzy and my legs get really weak and I feel like I’m going to pass out.”

Despite having only recently gotten her diagnosis, Sadie disclosed that she had been dealing with the illness for some time.

The Sweetest Thing star also shared, “I hate it for you my darling. I really hate it for you.”

She added, “I’m sad. But I love you and I know you’re going to be OK. And I’m here for you and I believe you. And thank you for bringing this to light and awareness.”

Applegate’s daughter whom she shares with her husband, Martyn LeNoble, recalled leaving her sixth-grade lessons to visit the nurse "multiple times a day."

According to Johns Hopkins Medicine, POTS, also known as postural orthostatic tachycardia syndrome, arises when the heart rate quickly accelerates after standing up from a seated or laying posture this disease causes tremors, nausea, and fainting.