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Silent Killer

One in 40 people carry a defective gene that causes SMA, the No. 1 genetic killer of children under 2, and most don't even know it.

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When Emily Green received a phone call regarding Spinal Muscular Atrophy (SMA), she was amazed. "How did you ever hear about SMA," she asked. Underlying Green's inquiry was a much larger question, and completely opposite of what she asked: Why hasn't everyone heard of SMA?

It's an important question when you consider these revealing numbers:

• SMA is the No. 1 genetic killer of children under the age of 2.

• One in 6,000 children will be born with some type of SMA.

• One in 40 people carry the gene defect that causes SMA.

• Offspring of two SMA carriers have a 25 percent chance of developing the disease.

• Offspring of two carriers have a 50 percent chance of becoming carriers themselves.

SMA is a genetic disorder in which motor neurons in the spine rapidly degenerate. Without the motor neuron cells, those who have the disease are unable to control voluntary muscle movement, which affects their ability to crawl, walk, sit, stand, breath, and swallow. Their muscles deteriorate and are of little use.

Green's 3-year-old daughter, Aubrey, has Type I SMA; it is the most severe form of the disease. Aubrey cannot stand or sit, she eats through a feeding tube, and she uses a ventilator at night so she can breathe. There is no cure for SMA, and Aubrey already has exceeded the two-year life expectancy of Type I children.

What form of SMA a child has usually is determined when symptoms first begin to appear. Those with Type I can begin displaying problems as early as the latter stages of pregnancy with reduced fetal movement. A postnatal sign for Type I is a baby's inability to sit up.

Milder forms of the disease manifest later, and these children generally have fewer problems and live longer. Kids with Type II SMA normally are diagnosed when they are between 3 and 15 months; they can sit, but are unable to stand or walk, and have respiratory problems. Those with Type III SMA will present symptoms later, usually between the ages of 2 and 17, and problems can include an abnormal manner of walking, difficulty running, and trouble climbing steps or rising from a chair. Gradually, with increasing weakness, Type III sufferers can lose their ability to walk. For children with these types of SMA, life expectancy falls within a broad range, and many live well into adulthood.

Aubrey was able to roll over as a newborn, but by 6 months of age, she still was unable to sit up. Although friends and family tried to console Green, a Luling native, jokingly saying that Aubrey was just a lazy baby, she decided to discuss her concerns with Aubrey's pediatrician. The doctor referred Green and her daughter to the Muscular Dystrophy Association (MDA) Clinic at Children's Hospital. Dr. Anne Tilton, pediatric neurologist and director of the clinic, ran a blood test for SMA. Aubrey tested positive, and Tilton diagnosed her with Type I at 7 months of age.

Tilton would have liked the diagnosis to have been made sooner. She advocates genetic testing for newborns, screening them for a number of inherited diseases including SMA. Louisiana does screen newborns -- Tilton says it's a fairly progressive screening compared to other states -- but it does not include testing for SMA. Tilton says the SMA test is considered too expensive to be run on every baby, and even if newborns are tested, there are other concerns.

"I think it's a great idea," Tilton says of testing newborns for SMA. "You can mandate it, but then you need to take it to the next step: make sure you're right and then have the resources to help those who test positive."

Green and her boyfriend, Josh Picou, are SMA carriers, but never knew it until Aubrey was born. Neither has the disease themselves, but each has a defective gene, which, when combined with another carrier, causes the disease. The only thing that might have tipped them off to the possibility of SMA would have been a family history of the disease. Green isn't aware of any, and Tilton says everyone has genes that are potentially problematic.

"Every person on earth probably carries four or five genes that in the right combination with another could cause severe disorders," explains Tilton. "When you do the math, sometimes you wonder how any of us are normal. But it's random assortments and combinations. When someone knows they have the abnormality, they can get genetic testing and family plan that way."

Finding out about their daughter's disorder was only the beginning of a new set of challenges facing Green and Picou. They had to decide on what kind of care Aubrey would receive and how far they were willing to go to keep their little girl alive. At first, it seemed the biggest question was whether or not to perform a tracheotomy on Aubrey and permanently place her on a ventilator. Some families choose this method in order to prolong their child's life as long as possible. Others prefer palliative care, or support care, where no extraordinary measures, such as a ventilator, are taken, and the children are treated for respiratory infections and discomfort as the disease runs its inevitable course.

Green and Picou were opposed to the tracheotomy, but they were interested in learning about other treatment possibilities. After exhaustive research on the Internet and talking to other parents with SMA kids, Green found out about non-invasive (non-surgical) ventilation. Instead of a standard ventilator, which requires no effort on the patient's part, there is the bi-pap ventilator, which utilizes pressure to force the child to take deeper and more oxygen-rich breaths. The bi-pap ventilator is used as needed -- kids are easily connected to the machine by placing a mask over their nose and mouth.

Dr. John Bach, medical director of the Center for Ventilator Management Alternatives at University Hospital in Newark, N.J., developed the technique and other therapeutic approaches: a cough-assist machine helps kids cough, allowing them to clear fluid accumulating in their lungs; and an amino acid diet. (According to Bach and others, SMA kids cannot process normal proteins, so they need the simpler amino acids, which require little digestion.)

Green and Picou chose to follow Bach's recommendations. The results aren't miraculous, but they are encouraging. It is a full-time, exhausting job taking care of Aubrey, and these treatments will not change her overall weakness -- she can't swallow and she can only turn her head slightly -- or the disorder's progression. She is, however, the only child more than 2 years old going to the MDA Clinic at Children's Hospital that hasn't required a tracheotomy. Unlike many SMA sufferers, she has never been hospitalized for an illness. And, most importantly, Aubrey is a very happy child, who adores The Little Mermaid movie and anything to do with princesses. She also is very bright and is enrolled in the home-school program through the St. Charles Parish public school system. SMA does not affect intelligence. Tilton's clinic diagnoses several new cases from across Southeast Louisiana every year, and the doctor says that even though these children are severely incapacitated, they possess a strong mental acuity.

"One of the distinguishing features with these newborns is how alert and bright they are," says Tilton.

Green agrees, saying that at 3 years old, Aubrey has taken charge of her daily needs. "She'll direct you how to take care of her," the mother says. "She'll say 'Mommy, I'm hungry so put on my feeding tube,' or 'Get my suctioning machine; I need to cough.'"

Although there is no cure for any type of SMA, there have been some promising breakthroughs recently. Scientists have identified the defective gene -- Survival Motor Neuron One (SMN1) -- that causes SMA. Children with the disease are born without SMN1, which researchers believe produces a protein that sustains the motor neurons. There is, however, another gene -- Survival Motor Neuron Two (SMN2) -- which SMA children do have, and it also produces the necessary protein, but much less efficiently than SMN1. Dr. Kathy Swoboda, a neurologist and head of Project Cure SMA, which is funded by Families of SMA, is experimenting with drugs to increase the amount of protein SMN2 produces. Other studies follow a similar path.

Swoboda is trying Valporic acid, a drug commonly used to treat epilepsy, combined with sodium phenylbutyrate in early phase clinical trials. The combination has been effective, especially in Type II and Type III children, who have more SMN2 than Type I kids. She has seen the most dramatic response in younger children, because their motor neuron deterioration isn't as extensive as in older children. Some Type II kids in Swoboda's study have been able to stand after taking the drug combination. She thinks someday there could be drug therapies that cure Type III SMA.

Unfortunately, Swoboda hasn't discovered anything that can reverse the decline of a Type I patient. "We're starting to have therapies to prolong their lives, but once the kids present the weakness, we haven't found something to turn them into Type II kids," she says. Swoboda believes the solution lies within stem-cell or gene therapy at an early stage, before the cells die.

Green lets Aubrey take the lead in managing her disease. She doesn't want to permanently ventilate her daughter, but if the time comes and Aubrey still has fight left in her, Green will have it done. Like her daughter, Green is a survivor and she is determined to be with Aubrey as long as she can. Only divine intervention will stop her, she says.

"God is going to have to take her from me because I'm going to do everything in my power to keep her."

For more information on SMA, contact Families of SMA (800) 886-1762 or visit the Web site www.fsma.org.

The "stander" used by 3-year-old Aubrey helps her body - with circulation and orthopedic issues such as bone - density and growth. The device also helps her to be at - eye level with other children, which is beneficial to her - socially and psychologically. - JOSH PICOU
  • Josh Picou
  • The "stander" used by 3-year-old Aubrey helps her body with circulation and orthopedic issues such as bone density and growth. The device also helps her to be at eye level with other children, which is beneficial to her socially and psychologically.
Auburey has Type I SMA, the most severe form. - JOSH PICOU
  • Josh Picou
  • Auburey has Type I SMA, the most severe form.

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