Justin Bieber Remembers The Late 'Mrs. Bieber' With 'Love'

Bieber remembers Avalanna Routh, who passed away on Wednesday, as 'one of the greatest spirits I have ever known.'

Justin Bieber remembered his late fan, 6-year-old Avalanna Routh, on Wednesday (September 26), shortly after news of her passing broke. Routh, dubbed Mrs. Bieber, died after her lengthy battle with a rare form of brain cancer.

Bieber tweeted his condolences as the term "RIP Avalanna" became a trend on Twitter. "just got the worst news ever. one of the greatest spirits i have ever known is gone," he wrote. "please pray for her family and for her. RIP Avalanna. i love you." He then tweeted out a link to a website with more information about the form of cancer Routh had been fighting called AT/RT (atypical teratoid rhabdoid tumor).

Avalanna's family confirmed her passing on her Twitter account only hours before. Their statement reads, "Our darling Avalanna went to Heaven this morning. Oh Avalanna, the brightest star - you took our hearts with you, our greatest Love."

The survival rate for AT/RT, usually found in the brain, is extremely low. Only about 30 new cases of AT/RT are diagnosed in the U.S. each year, according to the site. Currently there is no cure.

Bieber and Avalanna forged a friendship in early 2012 after he learned of her family's Facebook campaign to get her to meet him. The pair then made headlines back in February, on Valentine's Day, when he flew the fan out to New York to visit him and allowed "Today " show cameras to follow the encounter. "Hangin' out with a special little girl. #MrsBieber," he tweeted about the meeting. "That was one of the best things i have ever done. She was AWESOME! Feeling really inspired now! #MrsBieber."

He and Mrs. Bieber spent more time together back in June of this past year as he took her around New York City when he was making the rounds on his Believe album release promo, including stops on the "Today." "Basically, we talk on iChat all the time, and I see her on FaceTime," he said, before they shared that she called his mother her mother-in-law. She also appeared onstage with him when he played the Apollo Theater.

Bieber was not the only celebrity to shine light on Avalanna's illness. Jessica Biel spoke up for her during the Stand Up to Cancer telethon earlier this month.