LOS ANGELES (AP) — Dr. Arnold Klein once said, "Put me next to a patient, give me a needle and I'm really happy."

To which the man once known as Hollywood's "Dermatologist to the Stars" might have added: "Make the patient Michael Jackson and I'll be even happier."

Klein, who died Thursday in a Rancho Mirage hospital at 70, was a pioneer in the use of Botox and other injectable substances to improve personal appearance. For years, however, he was better known to the public as one of Jackson's closest friends.

It was a relationship that helped cement the doctor's reputation as the go-to guy for stars such as Elizabeth Taylor, Carrie Fisher and others who wanted work to make them look younger.

Jackson's friendship would ultimately prove a curse for Klein after the King of Pop died of a drug overdose administered by another physician in 2009, and it was revealed that Klein had been regularly injecting Jackson with the powerful painkiller Demerol.

An investigation found no trace of that drug in Jackson's body when he died and Klein was not implicated in the death, but the revelation permanently stained his reputation as one of Los Angeles' most prominent celebrity physicians.

So much so that Klein had largely fallen off the paparazzi and gossip tabloid radar until he died.

No cause of death was given by the Riverside County coroner's office, and no investigation was planned.

Klein's celebrity client roster once included entertainers such as Dolly Parton and Cher, powerful Hollywood executives, wealthy Beverly Hills socialites and even international royalty.

Klein's favorite patient was clearly Jackson.

He called the entertainer "my best friend" in a 2011 interview with The Associated Press, adding that he had joined Jackson and Jackson's children in celebrating the entertainer's last Christmas in 2008.

Rumors persisted over the years that Klein had fathered two of Jackson's three children with Debbie Rowe, a nurse who had worked for Klein and who had married Jackson. Klein denied it.

Klein met Jackson in 1983 when Klein treated him for a skin rash. He quickly became the entertainer's regular dermatologist, treating him for ailments that included the skin disease vitiligo that causes a patchy whitening of the skin.

Conrad Murray, another doctor who had been providing the powerful anesthetic propofol to help Jackson sleep, was convicted of involuntary manslaughter in Jackson's death.

During Murray's trial it was revealed that Klein often provided Jackson with Demerol to ease pain during his friend's treatments.

Klein told The Associated Press in 2011 that the publicity drove away some of his international clients and political bigwigs who didn't want photographers to see them entering his Beverly Hills clinic. But he insisted his Hollywood clientele stood by him. Fisher for one agreed.

The actress told the AP at the time that Klein was a brilliant and ethical doctor who never would have misused drugs and who helped her immensely with her appearance and self-esteem.

"It's like he's a painter but the brush is a needle," she said at the time. She was traveling Friday and couldn't be reached for comment.

Attorney Garo Ghazarian, who represented Klein during the Jackson death investigation, called Klein a larger than life figure who was engaging, outgoing, candid and funny.

"In my line of work in representing different types of clients I respect all of them and their right to representation, but I don't necessary like each and every one of them," the criminal defense attorney said. "But I really liked Dr. Klein. I really liked him."

Soon after the investigation Klein filed for bankruptcy and blamed it on theft and fraud by former employees. They denied it, saying it was the doctor's own profligate spending that helped lead to his financial woes.

At one time Klein owned huge homes in Palm Springs, Laguna Beach and Beverly Hills, drove expensive cars and sported pricey jewelry.

At the time of his death, he still maintained a clinic in Beverly Hills. It was closed Friday.

In a video from last year that's posted on his website, Klein demonstrates a successful procedure on a patient to smooth out the wrinkles and improve the look of her face.

"What you want is a person not to look done but to look natural and to look good and better and rested," he said.

He also reiterated what he told the AP in 2011: "All I'm trying to do is be the best doctor I can."

Information on survivors was not immediately available.

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AP Entertainment Writer Lynn Elber contributed to this report.