Rusty Mason, the woman whose struggle to help her son Rocky overcome a severe deformity was depicted in the film "Mask," is facing another deadly battle: Her other son, Joshua, 30, has AIDS.

Mason says she will fight for Joshua as hard as she fought for Rocky, who died in 1978, 10 years later than doctors had predicted. "If you know any of my story, you know I don't have any use for what doctors say," Mason, 49, said yesterday in San Francisco. "They told me Rocky was going to die before he was 6, and he lived 'til almost 17 doing some of the same things Joshua is doing now."

Those things include holistic medical techniques designed to keep him from succumbing to the illnesses that kill AIDS victims, his mother said. "What you believe, works. The universe will support anything you choose to believe." Hawkins Sues Over Dropping Backdrop

Sen. Paula Hawkins (R-Fla.) filed a negligence suit yesterday against a Winter Park, Fla., TV station for injuries she suffered four years ago when a backdrop fell on her as she was being interviewed in one of its studios. The suit beat the statute of limitations by one day.

Hawkins, 58, was briefly knocked unconscious Jan. 4, 1982, after a 28-pound, 6-foot-high wooden and canvas prop toppled onto her at the studio of WESH (Channel 2). She was hospitalized for eight days, after which she complained of neck and back aches, memory lapses and an inability to focus her eyes. In her suit filed in Orange County Circuit Court, Hawkins contends she still feels pain and cannot work as well as she could before the mishap.

She also charged that her husband has lost "the services of his wife and he has in the past and will in the future suffer a loss of the consortium and society of his wife."

"She is in traction practically every night," said an aide, Kevin Childers, and sometimes is in "acute" pain after a long day in the Capitol.

The suit asks for more than $5,000, the minimum amount that can be requested in a civil action. Bhagwan Watch

Indian guru Bhagwan Shree Rajneesh, who was deported from the United States in November after pleading guilty to two federal immigration law violations, arrived in Katmandu, Nepal, yesterday from New Delhi, saying he had come to see disciples who have been inviting him for years.

Rajneesh told reporters "it is too cold" in the northern Indian state of Himachal Pradesh, where he has been staying since his return to India. He said he might stay in Nepal or return to India, but either way, "It is in the Himalaya that I will be residing." Nepalese Home Ministry officials had no comment on Rajneesh's visit. End Notes

After 10 years under scaffolding, the Renwick Gallery was "unveiled" yesterday. Several hundred patrons, contractors and Smithsonian employes attended a reception at the gallery last night to celebrate "the happy end," a spokeswoman said. Among the guests were Secretary of the Smithsonian Robert McC. Adams and architect Hugh Newell Jacobsen, who restored the building's interior in 1972 . . .

Herbert von Karajan, director of the Berlin Philharmonic orchestra, has come to the United States for medical treatment, Wolfgang Stresemann, the orchestra's general manager, said yesterday. Stresemann declined to give any other details. Karajan performed on New Year's Eve when he directed the Berlin Philharmonic in a concert broadcast live on West German television . . .

Singer Billy Joel and model Christie Brinkley donned Groucho Marx noses and glasses before leaving New York Hospital with their daughter Alexa Ray Joel, born Sunday, but they did not escape notice by the vigilant paparazzi. Swaddled in a blanket, the infant was not wearing one of the disguises. -- Lisa Serene Gelb