Tim Conway, a 53-year-old radio disc jockey in Tucson, Ariz., was 19 before he had any idea what was causing the weakness and clumsiness that had plagued him since he was 12.

After years of being taunted by gym teachers and suspected of malingering in boot camp, he was finally told by a Navy doctor that he had muscular dystrophy in 1961. The diagnosis was refined to Becker type, with an uncertain prognosis, at an MDA clinic in Los Angeles the following year.

Dean Massey, 33, of Mount Pleasant, Tenn., fared better getting a diagnosis because he had two uncles with muscular dystrophy. But in the 1960s, doctors told the family they all had Duchenne dystrophy, which carries a different prognosis than Becker.

Even now, doctors outside the field don't always know what to expect of this stepchild of the dystrophies. As recently as 1993, 17-year-old Jason Vogel of Omaha, Neb., nearly died before his family was able to convince doctors that it was worth doing a heart transplant on someone with Becker dystrophy.

What do people with Becker say they feel? Relieved that Becker carries a less grim prognosis than some other dystrophies. Fearful about an uncertain future. And frustrated, with doctors, teachers, friends, sometimes even their own families, who don't always understand what the disease means in their lives.

SOME WORKING DYSTROPHIN

In the 19th century, French neurologist Guillaume Duchenne and English physician Edward Meryon described the disease that became known as Duchenne muscular dystrophy. Advances in medical care have prolonged the lives of people with Duchenne since the last century, but its basic course remains remarkably consistent: weakness and falling in childhood, starting in the toddler stage or shortly thereafter; a wheelchair in late childhood or early adolescence; severe respiratory problems by the early 20s, leading to death in the 20s or 30s. (Before antibiotics, lung infections often claimed the lives of people with Duchenne by their teen years.)

Even in the 19th century, doctors observed that the disease affected boys almost exclusively. Later, they would correctly guess that this is because the disease is carried on the X chromosome.

But there were some boys and young men who didn't follow the predicted course. They had something that looked like Duchenne, but it was less severe. Symptoms sometimes didn't appear until the teens or even later. Muscle weakness wasn't so great. People sometimes walked until well into adulthood, even into their 50s and 60s, with only the aid of a cane. Was this the same disease, but milder, or a completely different disease? Doctors disagreed.

In the 1980s, testing based on the new science of molecular genetics would prove both camps partly right. But long before that, in 1955, German geneticist Peter Emil Becker stated that Duchenne and Becker dystrophies resulted from defects (mutations) in a single gene on the X chromosome - different defects for each disease. This variant of Duchenne dystrophy took Becker's name even before his theory was proven right.

Boys with Duchenne, because of a genetic mutation in the gene for dystrophin, a muscle protein, produce virtually no useful dystrophin. Several different mutations can cause this disease, producing little variation in the disease itself. Boys with Duchenne have a more severe muscle disease than boys with Becker, who, because they have a different genetic mutation (again, several are possible), make some useful dystrophin.

The presence of some useful dystrophin in muscle fibers accounts for the relatively less severe, but less predictable, nature of Becker dystrophy. Variation in disease severity among people with Becker is probably due to varying amounts and types of dystrophin produced in their muscle fibers.

KNOWLEDGE, SUPPORT AND JUST DOING IT

People with Becker dystrophy had this to say:

• Stay informed.

"Stay abreast of the research in your disease," says Jason Vogel, now a 20-year-old sophomore at Creighton University in Omaha. "Some doctors just don't know. They can't know everything about everything. If my Mom hadn't stayed current in her research about Becker dystrophy, I wouldn't be alive today."

• Get and give support.

"I wasn't really able to deal with my dystrophy until a couple of years ago," says Tim Conway. "I was aware that there was a wheelchair in my future. That horrified me. I couldn't deal with that."

Conway found an MDA support group in Tucson that helped him change his attitude. "There were about five people there in wheelchairs who had been in them most of their lives. I listened to them talk, and they had more active lives than I did. I said, 'What's this? They're in wheelchairs and they're having more fun than I am.' They said, 'Take a load off.'"

With the help of the MDA group, a therapist and Adult Children of Alcoholics, Conway feels he's finally dealing with dark forces that have plagued him most of his life.

A lot of the trouble stemmed from his family's inability to deal with the problem, Conway says. "Differences were not OK. Being disabled was a difference, something that was not OK, so it wasn't talked about.

"If you've got kids, be there for them. Talk about it. Don't let them become isolated with their feelings, but be able to talk about it with them. Just asking how they feel would help."

• Do what you do best.

Vogel isn't sure about his college major. Right now, he thinks it'll be business. He's also in Ecology Now, a campus environmental group, and volunteers for MDA. "Creighton is handicapped accessible in almost all buildings," says Vogel, who can manage stairs, but with difficulty. "If a classroom isn't accessible, they work with me. They let me pick my schedule first, even before the seniors."

Conway started a career as a draftsman, but that was in the 1970s, long before computerized drafting, and the work was too physically demanding. A couple of years ago, while driving to California, he says, "Something popped into my head that I had buried all my life. I wanted to be a disc jockey. It was buried all those years. I realized I had been doing that stuff anyway. I'd go to parties at people's houses and the first thing I'd do was take over the record player. I was always making tapes for myself and for other people." He started classes at a Tucson radio station last June and now has a regular weekly show of his own.

The farm that's been in Dean Massey's family since 1929 and the woman he married 13 years ago are what sustains him. From time to time, he's thought about getting more education or working in town, but, he says, "I've got farming in my blood so bad, it's like a huntin' dog. It's got to be in your blood. I'm always reading farm magazines. We've got this little old book here that advertises farm equipment and cattle and stuff. If someone's looking for something, I'll see if I can find it. I really enjoy being on the farm. I couldn't live in town. I'd go crazy.

"He says his wife, Mary, who married him when she was 18 and he 20, does all the manual work he would do if he could. He says it doesn't strain the marriage. "If you really love one another, there's nothing going to stop you. And that's what the deal is with my wife and me."

Dr. Peter Emil Becker first theorized in the 1950s that Becker muscular dystrophy and Duchenne dystrophy are caused by different defects on the same gene on the X chromosome. Some 30 years later, genetics research proved him right.