When Stephanie Mason was 8 years old, her parents brought her down from Dayton, Ohio, to the annual symposium on short stature at Johns Hopkins. All ages, milling around and chatting. Her face lit up.

"Mom! Look! They're just like me!"

One American in 20,000 has achondroplasia, or dwarfism. It is a lonely thing. Nearly always, your are the only one in your high school or college. Paul Miller, a pre-law student at the University of Pennsylvania, is the only dwarf in 10,000 students. That is partly good -- everyone in the place knows him -- and partly bad -- it is also lonely.

When Frank J. Lentini heard there was a young woman dwarf in Watertown, N.Y., he went over right away -- an hour's drive from his native Auburn. He didn't know her name, even. But he asked around and soon found her, Emma Cronk, and called her up and later married her. (She died just last year, but there are two children, a girl, 25, a dwarf, and a son, 30, who is six feet tall.)

That's one of the great things about the short-stature symposium. The eighth one was held over the weekend in Baltimore. It began in 1972 as part of a plan to develop a national center for studying the medical problems of little people. But right away it turned into something else as well: a social occasion, a convention, a family reunion.

It doesn't take much imagination to figure out the problems and frustrations of being four feet tall. The furniture in your house, the chairs and tables, the kitchen counter, the cabinets, the windows shades: Everything's out of reach. Go to an office building, and you can't reach the top buttons the elevator. What about cars? In a crowd, say on the subway, you can literally get lost among all those midriffs.

But these problems are the easy ones. Lentini bought a house, renovated it, but never bothered scaling things down.

"I just use a kick stool," he says. "I move it around where I need it. You get accustomed to those things. You've gotta have patience."

There are worse experiences for a short-statured person than having to ask someone to push an elevator button. Even though Lentini has lived in the same town all his life and has worked for many years at the local bottling plant, he finds that some people are still prejudiced.

"You're sitting down on the job and three different people come along and knock your hat off your head -- the third time you feel like killing them. They see you're getting mad, and they say what's the matter, can't you take a joke?"

Voices from a teen-age workshop Saturday:

"You meet people and they're shy, they're afraid they'll say something wrong, or use the word 'short' or something. So I crack a joke to break the tension."

"I liked that song [randy Newman's 'Short People']. I don't care what they say. They tease me, I don't mind. I can't help it." (The psychiatrist-moderator gently asks if that is really how he feels about it, and the boy's head bows and his face closes and he whispers, "I don't care.")

"When you go to a shopping mall you're like the Pied Piper -- you get a whole group of kids trailing after you trying to figure out what you are."

"Friends? Basically, I have one kid I can trust. He's in the eighth grade, a year ahead of me, and we talk on the bus about what our day has been like. The seventh grade is a waste of time: we've been learning the same thing for the last three years."

"My parents overprotect me. When I go out, they give me the Twenty Questions bit. My sister can go out and they don't say a thing, just: 'Have a nice time.' But me: 'Don't get hurt, be careful, who you going with, who's driving.' It's not offensive, just monotonous."

"I'd rather have people dislike me for myself than pretend."

"Some people just don't like me. I came out for some clubs at school and they just said, 'Get outta here.'"

"My sister's here at the symposium but she went off somewhere. She doesn't want to be around."

"Kids don't think you can do a sport, can't do this or that. You have to show 'em up. I was the number one weight-lifter on our team for three years in a row."

"Yeah, I played baseball, got 32 walks in 14 games. When the other team hassles me, my team gets right behind me."

Dr. Victor A. McKusick, one of the world's authorities on genetic deseases, began concentrating on dwarfism in the '60s, has just been named honorary president of the Little People of America. In two decades, the field has more or less exploded -- his catalogue of genetic diseases, a basic sourcebook, has had four printings since 1966 as several dozen forms of dwarfism have been detected.

"In the '50s, all these forms were lumped together as limb or trunk deformities," he says. "But there are all sorts of variations. Some forms are transmitted by the parents, others are recessive and so aren't automatically handed down."

About one case of achondroplasia in four has come from the parents, he notes. It used to be one in five, but more dwarf couples are having babies, it seems. (Childbirth is always by Caesarean section.)

"There are new treatments, lots of little things we can do for the infant with the enlarged head, orthopedic problems [at least two dozen of the 400-plus people at the symposium were recovering from leg surgery or walked on crutches], also we are dealing with middle-ear infections, which they are prone to."

Down the hall, in the big assembly room, short-statured people were talking up a storm, with parents and brothers and sisters joining in. One remembered the words of Beth Lawson, a district director of LPA who spoke to the group earlier. As an eldest child, she was accepted completely by her parents and two brothers, she said, was given great confidence and stability, was treated just the way the books say.

"But you know, I wish we'd talked more. I mean, they understood what my feelings were, and they acted on them when it was called for, made sure I wasn't left out of things. I just wish we'd talked about it. Sometimes you need to tell a child it's okay to be unhappy."