When her 2-year-old daughter asks, "Where is Erin?" Barbara Trainor shows the child pictures of her baby sister.
Five-month-old Erin Marie Trainor died in February of spinal muscular atrophy, a disease that destroys the nerve cells responsible for voluntary movement. It is the No. 1 genetic killer of children under 2.
"Caitlin's memories of her sister come from ours," said Mrs. Trainor, 29. "I remind her of how she loved to sit with Erin and help me with her breathing treatments."
Now, in memory of the the child they lost, the Hampstead family has formed the Chesapeake Chapter of the Families of SMA.
"Her memory is so present to us," she said. "I think back to every day that Erin brought meaning to our lives. We want to help other families coping with SMA and bring public awareness to the disease."
Mrs. Trainor recalls every detail of the day in November when she and her husband, Eugene, learned of Erin's disease.
"I saw the pain in the doctor's eyes, when he told us Erin would not be with us long," said Mrs. Trainor. "If he could have told us about Families of SMA, it would have helped us and him. Doctors don't realize there is a national organization to help families."
Six weeks after her birth on Sept. 10, Erin was diagnosed with the acute form of the disease. She was unable to move her arms, legs and chest muscles.
The baby could smile, though, said her mother -- "with a smile that lit up a room."
"All her life was in her face," Mrs. Trainor said. "She comforted me that she was so bright and alert. God couldn't take away the horrible disease, but everyone could look at her without realizing she was ill."
The Trainors worried about the biopsy procedure, which confirmed the diagnosis. Erin awoke from the surgery with a bTC smile that comforted her parents.
"We never wanted to see her in pain," said Mrs. Trainor.
Although she knew the difficulties inherent in caring for the baby, Mrs. Trainor was determined to keep her daughter at home.
"We knew Erin's time with us was short and we wanted her to be part of everything," she said. "Every day was critical for us."
After a bout with pneumonia kept Erin in the hospital for three weeks in January, Mrs. Trainor pleaded with doctors to "teach me anything and everything I need to know."
"I wanted Erin home," she said. "I wanted Caitlin to enjoy her sister for as long as possible."
The Trainors felt the home atmosphere would lend quality to Erin's short life.
"We put a crib in the family room among Caitlin's activities," Mrs. Trainor said. "Caitlin even took part in Erin's chest therapy."
The family also relied on Carroll Hospice.
didn't want to use hospice because it was like giving up," she said. "But I found that, just as much as we did, they wanted to make Erin comfortable at home."
Erin died at home Feb. 18 -- "a beautiful day in the middle of winter," her mother said.
"The night before I had rocked her and told her if it was getting too tough for her, I wanted her to go in peace," said Mrs. Trainor.
The Trainors had always wanted to fill their Hampstead home with children. They know now that they both carry the recessive gene that causes SMA, so they run a one-in-four risk of having another SMA child.
"We are normal people that this stuff is not supposed to happen to," Mrs. Trainor said.
"If we have anger about anything, it is that we wanted more children," she said. "I don't want Caitlin to be an only child."
The anxiety has spilled over to other family members, she said.
"There are so many nieces and nephews," she said. "We are all scared somebody could pass this on."
They hope research will one day provide a cure for the disease.