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Coleman was taken off life support and died with family and friends at his side, Utah Valley Regional Medical Center spokeswoman Janet Frank said.
He suffered the brain hemorrhage Wednesday at his Santaquin home, 55 miles south of Salt Lake City. Frank said Coleman was hospitalized because of an accident at the home, but she had no further details.
Coleman's family, in a statement read by his brother-in-law Shawn Price, said information would be released shortly about his death.
Best remembered for "Diff'rent Strokes" character Arnold Jacksonand his "Whatchu talkin' 'bout?" catchphrase, Coleman chafed at his permanent association with the show but also tried to capitalize on it through reality shows and other TV appearances.
His adult life was marked with legal, financial and health troubles, suicide attempts and even a 2003 run for California governor.
"I want to escape that legacy of Arnold Jackson," he told The New York Times during his gubernatorial run. "I'm someone more. It would be nice if the world thought of me as something more."
A statement from the family said he was conscious and lucid until midday Thursday, when his condition worsened and he slipped into unconsciousness. Coleman was then placed on life support.
"It's unfortunate. It's a sad day," said Todd Bridges, who played Coleman's older brother, Willis, on "Diff'rent Strokes."
"Diff'rent Strokes" debuted on NBC in 1978 and drew most of its laughs from Coleman, then a tiny 10-year-old with sparkling eyes and perfect comic timing.
He played the younger of two African-American brothers adopted by a wealthy white man. Race and class relations became topics on the show as much as the typical trials of growing up.
"He was the reason we were such a big hit," co-star Charlotte Rae, who played the family's housekeeper on the show, said in an e-mail. "He was the centerpiece and we all surrounded him. He was absolutely enchanting, adorable, funny and filled with joy which he spread around to millions of people all over the world."
Coleman's family thanked fans for their continued support.
"Thousands of e-mails have poured into the hospital. This is so comforting to the family to know how beloved he still is," Price said.
"Diff'rent Strokes" lasted six seasons on NBC and two on ABC; it lives on thanks to DVDs and YouTube. But its equally enduring legacy became the troubles in adulthood of its former child stars.
In 1989, Bridges was acquitted of attempted murder in the shooting of a drug dealer. The then 24-year-old Bridges testified he became depressed and turned to drugs after "Diff'rent Strokes" was canceled.
Dana Plato, who played the boys' white, teenage sister, pleaded guilty in 1991 to a robbery charge. She died in 1999 of an overdose of painkiller and muscle relaxer. The medical examiner's office ruled the death a suicide.
"It's sad that I'm the last kid alive from the show," Bridges said.
Singer Janet Jackson, who appeared on several episodes of "Diff'rent Strokes," tweeted that, "I want to remember him as the fun, playful, adorable and affectionate man he was. He has left a lasting legacy. I know he is finally at peace."
Coleman was born Feb. 8, 1968, in Zion, Ill., near Chicago.
His short stature added to his child-star charm but stemmed from a serious health problem, kidney failure. He got his first of at least two transplants at age 5 and required dialysis. Even as an adult, his height reached only 4 feet 8 inches.
In a 1979 Los Angeles Times profile, his mother, Sue Coleman, said he had always been a ham. He acted in some commercials before he was signed by T.A.T., the production company that created "Diff'rent Strokes."
After the show was canceled, Coleman continued to get credits for TV guest shots and other small roles over the years, but he never regained more than a shadow of his old popularity. At one point he worked as a security guard.
Coleman played upon his child-star image as he tried to resurrect his entertainment career in recent years, appearing on late-night shows and "The Surreal Life," a VH1 show devoted to fading celebrities.
His role as a car-washing plantation slave in the 2008 conservative political satire "An American Carol" was cut from the final print. The actor also appeared in last year's "Midgets vs. Mascots," a film that pits little people against mascots in a series of silly contests for a chance to win $1 million. Coleman met with producers of the film earlier this year to ask them to remove a brief scene of frontal nudity that he says he didn't authorize.
Coleman was among 135 candidates who ran in California's bizarre 2003 recall election to replace then-Gov. Gray Davis, whom voters ousted in favor of Arnold Schwarzenegger. Coleman came in eighth place with 12,488 votes, or 0.2 percent, just behind Hustler magazine publisher Larry Flynt.
Running for office gave him a chance to show another side of himself, he told The Associated Press at the time.
"This is really interesting and cool, and I've been enjoying the heck out of it because I get to be intelligent, which is something I don't get to do very often," he said.
Coleman's health problems went beyond kidney failure. Last fall, he had heart surgery complicated by pneumonia, said his Utah attorney Randy Kester. In February, he suffered a seizure on the set of "The Insider."
Legal disputes also dogged him. In 1989, when Coleman was 21, his mother filed a court request trying to gain control of her son's $6 million fortune, saying he was incapable of handling his affairs. He said the move "obviously stems from her frustration at not being able to control my life."
In a 1993 television interview, he said he had twice tried to kill himself by overdosing on pills.
He moved to Utah in fall 2005, and according to a tally in early 2010, officers were called to assist or intervene with Coleman more than 20 times in the following years. They included a call where Coleman said he had taken dozens of Oxycontin pills and "wanted to die."
Some of the disputes involved his wife, Shannon Price, whom he met on the set of the 2006 comedy "Church Ball" and married in 2007.
In September 2008, a dustup with a fan at a Utah bowling alley led Coleman to plead no contest to disorderly conduct. The fan filed a lawsuit claiming that the actor punched him and ran into him with his truck; the suit was settled out of court.
In February — on his 42nd birthday — he pleaded guilty to a misdemeanor criminal mischief charge related to an April 2009 domestic violence incident at his home.
Coleman remained estranged from his parents, Sue and Willie Coleman, who said they learned about his hospitalization and death from media reports.
Sue Coleman said she wanted to reconcile and had been patiently waiting for her son to be ready.
"One of the things that I had prayed for was that nothing like this would happen before we could sit with Gary and Shannon and say, 'We're here and we love you,'" Sue Coleman said. "We just didn't want to push him."
She would not discuss the cause of the estrangement.