Muscle-Bound Boy Offers Hope for Humans

"All this work was going on the assumption that . . . it would have applications in humans. We were all going on the assumption that it worked the same way in humans," Lee said. "But there was no proof."

That changed with the birth of the unusually muscular boy in Berlin. Markus Schuelke, a neurologist at the Charite University Medical Center in Berlin, was called to the hospital shortly after the boy's birth. When tests determined there was nothing else wrong with the boy, Schuelke contacted Lee and his colleagues and another team at Wyeth.

A detailed genetic analysis and blood tests determined that the boy's myostatin genes were damaged, and that he had none of the protein circulating in his blood.

"This is now the first case of a human with a myostatin mutation that's been identified," Lee said. "We think this is quite important, because it says for the first time that myostatin does in fact play an important role in regulating muscle growth in humans. The implications are that people will be more optimistic about the possibility of targeting myostatin for human therapeutic applications."

As it turns out, the boy's mother, a former sprinter, has one damaged version of the gene. He has two. No other family members were tested, but several are reported to be unusually strong. One male relative, for example, was a construction worker renowned for his ability to unload heavy curbstones by hand.

It could turn out that subtle variations in the myostatin gene explain why some people are more muscular, stronger or more athletic than others, McNally said.

"We all know that we're a little different that way. This is a good candidate gene for modulating some of that," McNally said. "There may be more subtle mutations that only slightly affect muscle growth."

Several dietary supplements are already on the market that claim to affect myostatin and help build muscles. None, however, has been shown to work, Lee said, adding that he was concerned that if drugs become available that affect myostatin, they could be subject to abuse.

"Unfortunately, I think anything that we do along these lines to improve muscle mass in patients will almost certainly have the potential for abuse by healthy individuals," Lee said. "We're going to have to work hard to make sure these drugs don't get into the wrong hands. But the potential for helping patients in dire need is important. I think it would be unfortunate to focus on that and slow the research down."

It is unclear whether the boy, whose identity is being withheld, will suffer problems later in life. One fear is that the lack of myostatin could cause his body to use up its natural supply of replacement muscle cells prematurely.

"We fear it might happen that this regenerational capacity of the muscle might be exhausted too early," Schuelke said. "It's like an account you live on, and if you live on it too lavishly you don't have enough for old age."

But inasmuch as no one has ever encountered a child such as this boy or studied animals with defective myostatin genes into old age, his health -- and eventual strength -- remains unknown.

"We don't really know," Schuelke said. "We'll just keep observing him and making tests."