LOS ANGELES — 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 fathered two of Jackson’s three children with Debbie Rowe, a nurse who had worked for Klein and who 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.