In July 1994, Marcus Espino, then only 16 months old, was diagnosed with a fatal genetic storage disease called Muccopolysaccaridosis 1H, also known as MPS 1 or Hurler's syndrome. His parents were told that a bone marrow transplant (BMT) was his only chance for survival.

Hurler's syndrome is caused by the body's inability to produce a specific enzyme called alpha-iduronidase. Normally, the body uses enzymes to process proteins, sugars and other substances in tissues and cells as well as break down and recycle cells after the cells die. In children with Hurler's syndrome and other storage disorders, the missing or insufficient enzyme prevents this normal process from happening, leaving deposits in virtually every cell of the body. As a result, cells do not perform properly and may cause progressive damage throughout the body, including the heart, bones, joints, respiratory system and central nervous system, eventually leading to an early death.

"Ten years ago we didn't know any other families going through this," says Marcus' father, Rick Espino, a fire captain with the California Department of Forestry and Fire. But since Marcus developed Hurler's, he has become very involved with the MPS Society — a non-profit organization for families facing storage disorders. "We heard about a doctor in Minnesota who performed bone marrow transplants for kids with Marcus' condition. We were prepared to pack up everything and move there."

But then, the doctor in Minnesota referred the Espinos to Dr. Morton J. Cowan, a renowned BMT expert at UCSF Medical Center's Children's Hospital. In October 1994, Marcus underwent his first transplant at UCSF, receiving bone marrow from an unrelated donor, followed by chemotherapy.

Bone marrow transplants involve replacing diseased marrow with healthy marrow, injected into the bloodstream via an intravenous tube. The marrow may come from a healthy donor. The goal of the transplant is to replace unhealthy or destroyed bone marrow stem cells with normal bone marrow stem cells from a healthy donor. The transplant is performed following a conditioning regimen that includes high doses of chemotherapy and sometimes radiation.

Unfortunately, six months after Marcus' BMT, the number of donor cells in Marcus blood had dropped to a point that was too low to provide sufficient enzyme and as a result, Marcus began experiencing symptoms of Hurler's syndrome.

"While the number of donor cells stabilized at less than 10 percent, we felt that this would not be sufficient in the long-term to protect Marcus from the deleterious affects of Hurler's disease," says Cowan. "Since Marcus' body had already accepted the donor's cells, we felt that using the same donor would be the best approach." Following the advice of Cowan, the Espinos decided that the best chance for Marcus' survival was for him to undergo a second BMT in July 1995, using the same donor.

"It was a really hard decision," remembers Rick, who was told by some doctors that it was too dangerous to perform another BMT. "But Dr. Cowan had always been careful and conservative with Marcus' care and said he believed it would be a mistake for him not to have another BMT. So we trusted his opinion and never looked back."

The procedure saved Marcus' life. Now, more than ten years later, Marcus, who is twelve years old and about to enter the seventh grade at Rancho San Justo Middle School in Hollister, Calif., isn't much different from other boys his age. However, although the BMT helped to stop the progression of Hurler's syndrome, Marcus still suffered from severe damage to his joints and bones

"Despite all of the orthopedic problems Marcus has faced over the years, he has strived to be as normal a child as possible," Rick says. "He has played T-ball, youth soccer as a goalie, has learned to ride a bike, a scooter and even rollerblade, which scared the heck out of me and my wife!"

This is remarkable considering the numerous operations Marcus has undergone to treat some of the skeletal damage, especially to his legs, caused by Hurler's syndrome. At four years old, he had staples put inside his legs, just below his knees, to stabilize his severe knock-knees. At 10 years old, the staples were removed and placed above Marcus' knees. Although he did experience some improvement, this put tremendous strain on his kneecaps, which affected his hips and spine and his ability to walk.

As a result, Marcus underwent double hip surgery. At 11 years old, he also had his right foot corrected because his tendon was pulling his toes inward, causing them to curl. He had to be in a cast, then a brace, and then wore special orthotic foot ware to keep his foot from curling. Now, Marcus goes to physical therapy each week at UCSF where he performs exercises to help strengthen his legs. He also participates in occupational and speech therapy three times a week.

"While a transplant can be life-saving for children with Hurler's syndrome completely correcting many of the manifestations of the disease, the one area that is least benefited and sometimes most frustrating involves the joints, which tend to progress," says Cowan. "However, to have a young man like Marcus come to my clinic and have a normal conversation with him when you know that without a transplant he wouldn't even be alive today, is a most gratifying experience and makes it all worth the effort!"

And Rick couldn't agree more. "I'm still amazed at the things Marcus can do. Most parents worry about whether their son is going to make the baseball team and now I'm just happy that he can run to first base," he says. "Going through this with Marcus has made me immediately closer to him, and my daughter, Marisa."

Story written in October 2005.

Abby Sinnott is a San Francisco-based freelance writer.