Scott Hamilton, the world and national figure skating champion, received an unusual fan letter this week.

It was a photograph of a woman, tall and attractive. She had her hair mussed over her face so she couldn't be identified. She was sipping a glass of wine and wearing, well, nothing at all.

Here's what she wrote: "Dear Scott, I'll be your Susan Anton if you'll be my Dudley Moore."

"Wow," said Hamilton, rolling his eyes.

At 5-foot-3 and 110 pounds, Hamilton probably would have to look up to Moore, the movie star who turned being short into something enviable. And at 23, it's as tall as he's going to get.

His skating colleagues call Hamilton "Little Guy," but fans are big on his swashbuckling style. Among the onlookers at the Coliseum today, where Hamilton took the first step toward a successful defense of his U.S. figure skating title, was Jo Jo Starbuck.

"He's so down-to-earth," Starbuck said. "When I saw him at the hotel last night, he already knew the names of all the bellmen, the telephone operators and the guys from room service. He treats everyone the same--warm and friendly."

This is a rarity in this high-pressure sport, particularly from a national and world champion. But Hamilton followed a far-from-ordinary route to the catbird seat, so it's less of a surprise that he's a different kind of catbird.

He's one of two adopted sons of Ernie and the late Dorothy Hamilton of Bowling Green, Ohio. To his parents, skating was something you did with shoes that have wheels.

When he was 6 years old, Scott stopped growing. Doctors didn't know what to make of his illness, which combined severe respiratory problems with a partially paralyzed intestinal tract. But they knew it was serious. At one point it was diagnosed as cystic fibrosis. He was given six months to live.

But another opinion from a doctor in Boston gave hope, and somewhere along the line, Bowling Green built an ice rink. This pathetic wraith of a boy decided to give ice skating a try.

And ice skating cured him. "That's right," said his father. "Without knowing how or why, it cured him. The cool, humid atmosphere really helped his lungs, and the exercise helped him overall." Hamilton started growing again.

By the time he was 12, he was heading off to live with skaters in Illinois and study full time. By the time he was 17, he was national junior champion. In 1980 he carried the U.S. flag into the Olympic Stadium, an honor voted him by his teammates, who felt he embodied the Olympic spirit, even though he wasn't expected to win a medal and didn't. Then came his crowning achievement, double victories in the national and world championships last year.

Knowledgeable skating observers attribute much of Hamilton's success to his outgoing personality. "He plays to the audience," said Bob Mack, assistant director of the 1980 World and U.S. Figure Skating Tours, "and let's face it, judges are still audience, no matter how technical they get. He's dynamic. He has flair. He makes the audience feel like a part of the presentation.

"They see a little guy like him--so tiny--go up off the ice three or four feet. They're just in awe."

Today, in the first phase of Hamilton's U.S. title defense, he showed a little of how appealing the crowds find him. It was the compulsory figures competition, where each of the 10 top U.S. skaters must perform three specific figure-8 maneuvers. The tracings are checked in minute detail by nine judges.

On the second set of tracings, Hamilton picked a bad patch of ice. At the top of his figure-8 his skate practically stopped and he shook like a windblown sapling until he regained momentum.

A sigh came from the sparse crowd. And the tableau was repeated each time he traced over that spot.

In the end the judges checked the ice, discovered a bad flaw and permitted Hamilton to reskate the figure, which is unusual. He went on to win the event, which counts for 30 percent of the total score in the three-day competition.

On Friday the senior men will compete in the set program, which counts for 20 percent of the total score, and on Saturday they will perform the free skate program, which comprises the remaining half.

Hamilton is considered a safe bet to retain his title. Traditionally the champion, as in boxing, has to be soundly defeated to lose his title. "He'd have to beat himself," said Hamilton's coach, Don Laws. Laws a graduate of Gonzaga High, is the only Washington, D.C., native ever to win the national title, which he captured in 1950.

Assuming Hamilton succeeds here this weekend, he will have fulfilled one-third of the remaining goals he has set for himself. Next will be successfully retaining the world title later this winter in Copenhagen. Then he must hang on until 1984 to win the Olympic medal that eluded him in 1980.

"He told me he doesn't care what kind of medal it is," said his father. "He just wants one. After that, I guess he'll go pro. He can pretty much write his own ticket with one of the shows."

Hamilton calls his skating experience thus far "a dream. I've gotten back from skating two times what I put in. Everything that's happened to me has been like a dream. Carrying the flag in the Olympics, winning the nationals and the worlds, being named the (1981) U.S. Olympic Committee athlete of the year, and getting nominated for the AAU Sullivan Award. What an honor."

"But," he said, "I'm still trying to keep it in perspective."

Then he and his father and his coach and his friend Starbuck trundled out of the arena to celebrate his victory in the compulsory figures.

At Pizza Hut.