Exceptional Parent Magazine Sept. 2003
Living With Pompe's Disease
By Julia Steele Reid
What is Pompe's Disease?
People with acid maltase deficiency (AMD), or Pompe's disease, lack an enzyme that is required to break down glycogen in the lysosome, the part of the cell responsible for "recycling" various materials. Since glycogen cannot be broken down for reuse, it accumulates within the lysosome. Over time, the lysosomes swell and begin to disrupt normal cell function. Although various types of cells may be affected, the most dramatic effects of Pompe's disease are seen in muscle cells, resulting in muscle weakness and dysfunction.
There are three forms of Pompe's disease: infantile-onset, juvenile-onset and adult-onset. Typically, the disease causes the most damage in infantile, or early-onset, cases. In these cases, the muscle most directly affected is the heart-which can become up to three times the size of a typical infant's heart-though low tone and a "weak suck" resulting in feeding problems are also characteristic. Other common symptoms include an enlarged liver and/or tongue. Most babies with Pompe's die before they reach their first year, often of cardiorespiratory complications.
In juvenile- and adult-onset cases, such as Eric Hamlin's, the heart is not usually affected in so drastic a manner. Rather, muscle weakness in the arms, legs, torso and respiratory system is the primary symptom of the late-onset forms, and the disease tends to progress much more slowly in these cases. In all cases of the disease, however, the most important thing is to identify the condition early and accurately. Sometimes, this may mean getting a second opinion-a lesson the Hamlin family learned well.
What Signaled a Problem?
David and Kathy Hamlin knew that their son, Eric, had started walking a bit late (just before age two) and walked a bit oddly. Still, they didn't think much of it until one day when David took Eric with him to a doctor's appointment. Eric was three years old then.
The doctor noticed Eric's waddle and suspected a hip problem, so he suggested that the Hamlins see an orthopedic specialist. They did so, but the orthopedic specialist suggested yet another step: taking Eric to a neurologist.
At the neurologist's office, Eric was asked to perform simple tasks such as writing his name, drawing a circle and a square, etc. "And then in front of all of us," says David, "without any testing or anything beyond the four little written tests, [the neurologist] said, 'Well Eric's got Duchenne muscular dystrophy. ... We were floored."
Naturally, the Hamlins did the first thing any parents would do: they burst into tears. But then they collected themselves and went home, and soon afterward they took the important step of picking up the phone to speak with another doctor. Dr. Susan Winter, who specializes in rare genetic conditions, did not agree with the neurologist's diagnosis. While she admitted that Duchenne was a close match for Eric's symptoms, she didn't feel that it was close enough, and suggested a muscle biopsy. When the biopsy results came back, the diagnosis was definitive: glycogen storage disease type II-Pompe's disease.
What Comes Next?
With the proper diagnosis finally in hand, the Hamlins were ready to learn more. A doctor in New York recommended a diet and exercise program for Eric that was intended to control the amount of glycogen in his body. The diet consisted of high-protein, low-carbohydrate foods, and each meal was supposed to be followed by 20-30 minutes of brisk exercise to work off excess carbohydrates before his body could store them. It was difficult at first for the Hamlins to persuade their three-year-old to follow such a regimen, but over time Eric learned to adhere to the program.
To address Eric's existing muscular issues, the Hamlins tried ankle-foot orthoses (AFOs) but eventually opted for heel-cord lengthening surgery, since Eric was loathe to wear the braces. These procedures helped him stop walking on his tip-toes and for the next several years Eric was able to walk with a more typical gait, though he now uses a wheelchair.
The Hamlins also decided to start an organization called the United Pompe Foundation, which helps families meet the cost of medical care or purchasing a wheelchair for their child with Pompe's.
What the Future Holds
In terms of treatment, hope is on the horizon. Researchers have been developing an enzyme replacement therapy, which is now in the clinical trials stage. Progress continues steadily, but has been slightly slower than it might be; because Pompe's disease is so rare, funding is equally so. Manufacturing the enzyme necessary for replacement therapy requires a lot of resources, including time and a large manufacturing facility.
For these reasons and others, trials currently include only infants with early-onset Pompe's, since these are the most critical cases and therefore the most likely to show life-saving improvements in condition. In the future, however, as the enzyme becomes more readily available, it is likely that trials will expand to include juvenile-onset cases as well.
Dr. R. Rodney Howell, of the University of Miami School of Medicine, is enthusiastic about the treatment. "As somebody who's been seeing Pompe's disease for many, many years and basically giving people such bad news, to see a treatment coming on the horizon is very exciting to me," he says.
Another factor in improving the quality of life for people with Pompe's is the ability to identify the condition as early as possible. Currently there is no new-born screening technique available, though prenatal techniques such as amniocentesis can be used to identify the disease in children known to be at risk (if an older sibling has been diagnosed with Pompe's, for example). Still, research is being done in this area and the hope is that a screening technique will eventually be developed.
What Parents Should Know
Dr. Howell's advice to parents is to be aware of any potential "floppiness" in infants, especially if it is accompanied by feeding trouble or other symptoms of Pompe's such as an enlarged tongue. Dr. Howell also points out, however, that parents should not panic if their baby seems a bit limber or reluctant to feed. There is a lot of variation in child development, he says, so the best thing is just to make sure that the pediatrician and family are all comfortable with the child's progress.
David Hamlin stresses the importance of parents getting involved in their child's medical care. He encourages parents to press for second opinions, do the research to stay informed and pay close attention to symptoms. And perhaps the most important thing of all for parents is to never give up hope.
For more information on storage disorders and enzyme replacement therapy, visit www.genzyme.com.
ENZYME REPLACEMENT CAN HELP
Jacob Slawson and his sister Samantha are feeling better-much better-thanks to a newly approved treatment for the genetic disease they both have: mucopolysaccharidosis type one, or MPS-I.
MPS-I, like Pompe's disease, is a lysosomal storage disorder caused by the deficiency of an enzyme. While different enzymes are missing in each disorder, there are some similarities: they both occur in varying degrees of severity, they both affect organs on a cellular level to the point of impairment and they can both be treated with enzyme replacement therapy.
An enzyme replacement therapy for MPS-I called Aldurazyme was approved by the Food and Drug Administration (FDA) in May of this year, and so is now generally available to MPS-I patients, of whom there are three or four thousand worldwide. The treatment involves receiving weekly IV drips of an enzyme serum that take several hours to administer in a hospital. But according to Tami Slawson, it's worth every ounce of time and energy.
Tami's children, Jacob and Samantha, are both affected by Hurler-Scheie, the moderate form of MPS-I (Hurler is the severe form and Scheie is the mild form). As in Eric Hamlin's case, it took a series of diagnoses before a lysosomal storage disorder was identified and confirmed as the culprit. The doctors guessed at a form of muscular dystrophy, but when that was proved false the diagnosis was changed to "rare progressive neuromuscular disease of unknown origin."
After two years of unproductive blood and tissue tests, a resident doctor happened to run a test for MPS. Surprise! It came back positive. Even with a confirmed diagnosis in hand, however, the next step wasn't clear. In the absence of treatment options, the Slawson family started an annual walk/run in the Los Angeles area to raise funds for MPS research (http://www.mpsrun.com).
Now, however, with the approval of Aldurazyme, Jacob and Samantha are beginning to find relief from some of their symptoms. Jacob's headaches are greatly reduced. Samantha's hands are functioning better. And with every new enzyme dose that's infused, so is a little more hope.
Reproduced with permission of Exceptional Parent Magazine. Further reproduction or distribution is prohibited without permission.
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