Comedian Jerry Lewis says he was surprised to reel in $1.2 million more in this year's annual charity drive than he did in 2007.  His annual 21 ½-hour telethon helps fund research and care for people with muscular dystrophy, a group of 40 hereditary diseases that causes a patient's muscles to progressively weaken.  

"Each year I tell myself, 'This has got to be it. There's no way we can do better.' Then, the following year, I'm astounded to see that generosity driven by love and compassion has a greater capacity than I thought possible," Lewis said in a press release posted on the Muscular Dystrophy Association Web site. "I am awed and humbled by this response."

Between one in 3,500 and one in 5,000 children are born with Duchenne or Becker muscular dystrophy, the most common forms of the disease, each year, according to the National Institutes of Health. Patients with the Duchenne variety typically display symptoms during early childhood, and only live into their 20s; those with Becker or other, milder forms of the disease, can stay healthy until adolescence and live into middle age. 

We asked Bob Marion, chief of the division of genetics and developmental medicine at the Children's Hospital at Montefiore in the Bronx, N.Y., to fill us in on the disease and any new treatments on the horizon. 

What is muscular dystrophy? 

It’s a group of diseases that share an abnormality in way the muscle cells work. Some are congenital, where the child is born with problems. Other forms don’t present until adolescence or young adulthood. All involve problems in the muscle cells but have different inheritance patterns.  

Duchenne muscular dystrophy is the most common. It usually occurs in boys and doesn’t present until between the first and third years of life. This is an X-linked recessive disorder, so it's carried by mothers and passed to sons. Each son has a 50 percent chance of being affected, and girls usually aren’t affected. The children typically are normal at birth and hit normal developmental milestones during their first year. They tend to start walking but develop muscle weakness in the part of the limb closest to the trunk, the proximal muscles. A tale-tale sign: They have a peculiar way of getting up. If they're sitting on the floor, they climb up on themselves. They have to grab their legs and push off a number of times to get up.  

Their thighs look very large, like they're muscular, but they're not: it's pseudo-hypertrophy of the calf muscles. What's actually happening is that the muscle cells are breaking, are being destroyed and they're just not working right. They have a slowly progressive problem where they become weaker and weaker. In most kids with Duchenne muscular dystrophy, they can walk till they're between 10 and 15, when the weakness kind of overwhelms them. [That loss of mobility is] associated with an illness where they're in bed a couple weeks and never regain the strength they lost. They spend the rest of their lives in wheelchairs with a host of medical problems. Most die in their 20s of heart or respiratory problems associated with the condition. It's very painful to watch them because there's not a lot of treatment for it.  

Has the prevalence of Duchenne changed with the advent of prenatal screening? 

No. It really hasn’t decreased. A woman with a family history can know during her pregnancy that she's carrying a fetus with muscular dystrophy. It's due to a mutation in a gene on the X chromosome, the dystrophin gene. Dystrophin is an important component that strengthens muscle fibers in the bones and heart and protects them from injury. Boys with this mutation on their X chromosome don’t make an adequate amount of dystrophin, and that's why the cells don’t work properly. We can identify the mutation during amniocentesis [but] it's not typically screened for in families in which it doesn’t exist. A third of the time it doesn’t run in families and, also, a lot of people continue the pregnancy even after amniocentesis with abnormalities.  

Are there any new treatment advances? 

There has been considerable effort in recent years to safely introduce a dystrophin-producing gene into muscle cells to try to prevent or reverse the condition; money raised in the telethon has been used to further this research.  

What about other treatments? 

There are things that have been used for years, such as physical and occupational therapy to keep the muscles strong as long as possible.  

This is an edited transcript.