Some of the signs pointed to a metachromatic leukodystrophy, or MLD, and the couple decided to attend a conference of the MLD Foundation in Hunt Valley in early June of last year.

Paul said it opened his eyes "just enough, just to the point where we didn't want any more information" on a "rare disease — degenerative, progressive and no known cure."

As they continued into the summer without a definitive diagnosis, Darlene drove to a doctor in Philadelphia to deliver a sample and pleaded with the doctor to deliver a diagnosis. The next day, they packed the car for a trip to Bar Harbor, Maine, and the doctor called back with the diagnosis.

Laura had MLD, a disease in which the body lacks an enzyme that breaks down buildup on the myelin sheaths that protect neurotransmitters.

Dr. Gerald Raymond, who has been treating Laura at Kennedy Krieger, said the disease eventually affects motor abilities, cognitive abilities and hearing.

Upon their return home from Maine, the family began to live by a new creed: Enjoy today, plan for tomorrow. Paul put in double railings on the staircases and grab-bars in the bathrooms. Eventually a ramp was built outside and a stair-glide was installed in to give Laura access to the second floor.

Those were accommodations for comfort and practicality's sake. Medically, there was one option.

There's no known cure for MLD, but Dr. Raymond said most success in utilizing bone marrow transplants to slow the disease occur in young adults. If a match is found and the transplant takes hold, the patient's cells are replaced by those with the enzyme that can protect the myelin and slow the disease's progress.

The Glaudemans didn't have to look far to find a suitable donor.

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As young girls, the 18-month difference between Emily and Laura was hardly an obstacle. The sisters were inseparable, striving to dress alike and spending endless afternoons on their backyard playscape and trampoline. As adolescence came, the girls who shared bunk beds as toddlers began to fight all the time.

Yet when their parents explained the diagnosis to Emily and Tim, both immediately volunteered to do whatever was necessary. Emily, it turned out, was a perfect match to donate bone marrow.

She thought back to a childhood memory when Tim, sensing that Laura was riding her bicycle too close to traffic, jumped out into the road, held out his hand and stopped the oncoming cars. Tim was convinced he had saved Laura's life that day. Now, it was Emily's turn.

"I'd do it 100 more times if I had to," Emily said.

The transplant took place on Sept. 16, 2011, after Laura underwent a round of chemotherapy at Hopkins, which was designed to suppress her immune system and prevent it from fighting Emily's cells.

Emily was discharged from the hospital that night, though the holes drilled in her hip to access her marrow laid her up for several weeks. It took several months for her to feel normal again. She returned to work and after caring for her sister for nearly a year, she plans to return to school this spring.

Laura spent 24 days in the hospital after the transplant. Darlene spent much of her time there during that time as well. The family would leave a cooler on the front porch so family and friends could drop off meals for Paul to heat up when he got home from work and also to bring to the hospital each night. Others gave gift cards for local restaurants, allowing Paul to pick up dinner on the way home.

When Laura left the hospital in early October, doctors recommended that she stay home as much as possible while her immune system rebuilt. A short time after her return home, the family received good news from her doctors: The transplant was a total success and 100 percent of Emily's DNA had taken hold in Laura.

"I feel like we're almost the same person now," Emily said.

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