Gary Coleman, the diminutive, wisecracking child star of the sitcom “Diff’rent Strokes,” whose adult life collapsed into a tabloid calamity, died Friday at a hospital in Provo, Utah. Coleman was 42 and suffered a brain hemorrhage after falling at his home in Santaquin, Utah.

Coleman was 10 when he stepped into the national spotlight in 1978, playing the witty, lovable Arnold Jackson on NBC’s “Diff’rent Strokes.” The role was created for him and made Coleman the best-known child star on television for the eight years the hit comedy was on the air.

He played the younger of two orphaned black brothers adopted by a white Manhattan millionaire after the death of their mother, the rich man’s housekeeper. The show was a comedic showcase for Coleman, who looked younger than his actual age because his growth had been stunted by a congenital kidney condition.

On the set, he proved to be a thorough professional who could memorize his dialogue in a single reading and deliver it with perfect timing. His signature line, directed toward his brother Willis, played by Todd Bridges, became a nationwide catch phrase: “What’chu talkin’ ’bout, Willis?”

“The true star of the show is 10-year old Gary Coleman as 8-year-old Arnold,” Washington Post TV critic Tom Shales wrote when the show premiered, calling Coleman “a most unusual tot with a strikingly professional comic delivery.”

Newsweek pronounced him “NBC’s Littlest Big Man” and “possibly the most original vid-kid since Howdy Doody.”

The show was such a cultural touchstone that first lady Nancy Reagan appeared on “Diff’rent Strokes” in 1983 to make an anti-drug pitch.

Coleman also had his own Saturday morning cartoon show and was a guest on “The Tonight Show,” where he upstaged Johnny Carson, who jokingly asked if he wanted to take over the rest of the show.

“With all the laughing and cheering out there,” he replied, “quite possibly.”

As Coleman’s salary rose from $1,500 to $70,000 an episode, his fragile health continued to deteriorate. He had undergone two kidney transplants by the time he was 14, and he was on dialysis while taping “Diff’rent Strokes.”

When the show was canceled in 1986, he was 18 and had amassed a personal fortune estimated at $18 million. But his life quickly devolved into a sorry spectacle of lawsuits, countersuits, recriminations and hurt feelings.

He sued his parents and advisers for taking money from trust funds meant to support him as he grew older. In court, his parents charged that Coleman had been brainwashed by a manager and was not competent to handle his affairs. In the end, Coleman won a $1.28 million settlement, but his relationship with his parents was all but fractured.

Now an adult with two failed two kidneys, the 4-foot-8 Coleman was becoming increasingly embittered and unemployable. He found occasional work in film and TV, but mostly he watched his money slip through his hands. At one point, his father said, Coleman tried to run him over with a car.

By the late 1990s, his life was crashing in a sad, gossip-fueled tailspin. He continued to have health problems, including heart surgery in 2009 and a series of seizures.