Strong boy offers hope for muscle disorders

A boy born with very well-developed muscles has inherited a double dose of a genetic variation linked to unusual strength in mice and cattle, German researchers report. The team, based at the Charite University Medical Centre in Berlin, say their findings could help develop new drug treatments for inherited muscle wasting diseases. But other scientists are concerned that the same drugs might also be used to enhance the performance of athletes.

The Berlin team leader, Markus Schuelke, said that the boy's unusual muscles were noticeable as soon as he was born - they were bulging and well-defined, especially in his thighs and upper arms. The boy's mother is a professional sprinter, and other members of his family are muscular, which suggested an underlying genetic basis for his strength. The scientists focussed on a gene that makes a protein called myostatin, which previous research showed is inactive in 'double muscle' Belgian Blue cattle, and so-called 'mighty mice'. The boy, now aged four, is otherwise normal, and completely healthy.

The study, published in the New England Journal of Medicine, showed that the boy's mother had one inactive copy of the myostatin gene, while her son had inherited two inactive copies. It appears that myostatin controls normal muscle growth, raising hopes that myostatin-blocking drugs could be used to encourage muscles to grow. The US Company Wyeth Pharmaceuticals is already carrying out safety trials of such a drug, called MYO-029, and is also planning a study with muscular dystrophy patients. Doctors think that myostatin blockers could also be used to treat an age-related muscle loss disorder called sarcopenia.

However, a commentary accompanying the study, written by geneticist Elizabeth McNally, sounded a note of caution, saying that although the findings hold great promise for treating muscle disorders, 'the potential for abuse outside of the medical arena is substantial, and further studies of the safety, efficacy, and long term consequences of manipulating muscle growth are needed'. McNally also said that in the future, people might have their myostatin genes tested, to help them decide whether or not to train as professional athletes.