At two months old, it's too early to say if Andrew Michael will take after his grandpa in most respects. Whether he'll have the same affinity for photography, or easy approach to life's challenges.

What Andrew does have in common with his grandpa, James Addie, is hemophilia. Addie, 53, was diagnosed early in his life with the inherited bleeding disorder; his older brother also has it, as does his nephew. Now, so does his baby grandson.

For Addie, the disease has meant years of bleeds, progressive joint damage, eventually the replacement of his left knee and both hips. Contaminated blood used for treatment decades ago left Addie with HIV, not uncommon among those his age with hemophilia.

But Addie's got a reason to be optimistic that things will be different for Andrew. In fact, Addie is the reason.

Four months ago, he traveled from his home in St Louis to the University of Michigan to get a single treatment he hoped would change his life — and that of his baby grandson. So far, it appears that it has.

Addie is in a clinical trial of a gene therapy for hemophilia developed by biotech BioMarin Pharmaceutical. It is an experimental treatment that uses a virus to deliver a healthy copy of a gene to make up for one that causes his excessive bleeding. The goal: to effectively cure the disease with just one administration, righting the genetic mistakes that afflict the families of 400 babies born in the U.S. each year.

"The hope with gene therapy is that we can get people to that place where hemophilia's not something that they wake up in the morning and think about first thing," said Dr. Catherine McGuinn, director of the hemophilia treatment center at Weill Cornell Medical Center. "I think of it as a way to protect people sort of every moment of the day."

The current treatment for hemophilia requires patients get infusions every few days with medicine that helps their blood clot, known as factor replacement therapy.

It's a dramatic improvement from treatment years ago. Addie remembers getting severe bleeds once or twice a week before he started prophylactic therapy. Once he started factor replacement every three days, he estimates he only had three bleeds per year.

Still, said McGuinn, "it is pretty onerous to think about finding a vein and doing this as part of your routine a couple of times a week."

Gene therapy would change that. And, in the four months since his treatment, it has for Addie.