Celine Dion came forward with a rare illness that hampered her ability to sing, which blindsided everyone, including her very own sister.

According to Hello, Claudette, Dion's sister, opened up about the singer's stiff-person syndrome diagnosis, which she initially thought was a different condition.

"Firstly, I always say that if Celine wasn't well, we would know about it. It would be impossible for her not to tell us," she said.

"Secondly, she wouldn't have postponed her shows, she would have canceled them. These have just been postponed," she continued.

Then she eventually admitted that she thought that Dion was just going through menopause. "I've told her - you're just being menopausal, calm down."

The National Institute on Aging described menopause as the point wherein a woman has stopped menstruating for 12 whole months.

Signs that indicate a woman might be experiencing the menopausal transition include hot flashes, lowered energy, disturbed sleep, and more, the Mayo Clinic noted.

This transition period begins in varying ages for different women, but the range lies between ages 45 and 55, and according to reports, the "The Power of Love" singer is currently 54 years old.

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Misdiagnosis?

Dion might have shared some of her stiff-person syndrome with her sister, and Claudette thought it was simply menopause.

Claudette added, "It's true that she does have muscle spasms; I've seen her myself with her little leg all twisted.

"Several people who know Celine well after working with her often ask me whether the iconic Caesars Palace stage slope might have damaged her nerves or the muscles in her pelvis."

Despite the rare disorder, Dion's sister reassured fans that the singer is being taken care of, and can still return onstage to perform.

"She is being looked after, she's getting plenty of massages, she's making the most of it and being pampered. She's going to return to the stage, I've heard that rehearsals are finished and it's going to be crazy."

According to reports, the stiff-person syndrome is also known as Moersch-Woltman syndrome, and is a "rare neurological disorder with features of an autoimmune disease."

Furthermore, since the disorder is so rare, it is reportedly often misdiagnosed as other autoimmune disorders.

Or perhaps for a person with no medical background, like Claudette, it could be misjudged as some other illness or condition altogether.

As of this writing, the "My Heart Will Go On" singer has canceled and postponed several shows. Recent reports note that the singer lamented her disorder, "Unfortunately, the spasms affect every aspect of my daily life," which makes performing difficult.

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