Five-month-old Avery Lynn Canahuati died Monday of complications from spinal muscular atrophy. Upon learning that their daughter had less than 18 months to live, Avery’s parents wrote a bucket list of activities for her to complete in her life and launched a blog about it last month. The list included items like “have a bad hair day,” “eat a cupcake,” and “play with Play-Doh.” The blog quickly went viral, making Avery a minor celebrity and earning her nicknames like the “bucket-list baby.” As of Tuesday, the blog had more than 2.4 million page views and counting. But what exactly is this disease?
What Causes SMA?
SMA is caused by a defect in the Survival Motor Neuron 1 gene (SMN1), a gene vital to the creation and health of motor neurons. The disease results in a loss of nerves in the spinal cord and weakens all muscles connected to those nerves. Eventually, the muscles become atrophic. Kenneth Hobby, the president of Families of SMA (a research and support organization with chapters throughout the U.S.) describes it as a “disease of nerve cells in the spinal cord. When they die off, your brain can no longer communicate with the muscles.”
How rare is it?
SMA is not as uncommon as one might think. In fact, it is the most common genetic cause of death in infants and toddlers, according to the Spinal Muscular Atrophy Foundation. Roughly 1 in 50 people carry the SMA gene, and if both parents have the gene, then all of their children have a 1 in 4 chance of getting the disease. Despite the seemingly high number of carriers, it is a rare, because a child can only get it if both carriers have the disease. Between 1 in 6,000 and 1 in 10,000 children are born with disease. SMA is sometimes referred to as “Baby ALS,” because the incidence rate is so similar to cystic fibrosis and ALS. But Hobby explains that there are fewer people suffering from SMA simply because of the shortened life expectancy.
What are symptoms?
Generally, babies with the disease will appear normal when they are born and will not experience symptoms for at least several months depending on the severity of their condition. The most common symptom is muscle weakness. The proximal muscles, those close to the chest, will be the most severely impacted and experience the greatest weakness. Because these muscles are involved in respiration, babies often have trouble breathing and are more at risk for respiratory infections. The distal muscles, those further away like the hands and feet, are less likely to be less affected. Though when weakness does find its way into the extremities it is usually worse in the legs than the arms. Interestingly, the disease has no impact on cognition or emotional development, so patients who live beyond infancy, can have a relatively normal life aside from physical ailments.
Of course, when the disease’s primary symptom is muscle weakness, it is particularly difficult to detect in an infant who would show few signs of moving on its own even during normal development. Hobby says it is a bit of a sliding scale, but the main indicator is that the child “will miss milestones like rolling over or moving their legs and they will develop a general weakness.” Even this gauge is not easy to use, and Hobby says that diagnosis can often be delayed because some doctors will suggest that babies are simply being “lazy.” However, once the possibility of SMA has been established, there is a very clear diagnostic blood test that will determine the presence of the disease.
SMA can come in several different types, which differ in severity and life expectancy. Type IV only affects adults over the age of 35 and the symptoms will eventually affect muscle movement and in particular walking. Type III patients will sometimes have trouble walking, are at risk for respiratory infections, and may experience muscle weakness, but they do not have a shortened life expectancy. Type II symptoms usually emerge before the child is 18 months. Patients with this type are not able to walk unassisted, but they can usually sit without help. Some sufferers will die in childhood, but the majority with this type will live to adulthood. Type 0 babies can show symptoms in embryo form, they are weak when they are born and are never able to breathe independently.
Type I is very severe. One of the things that makes this form so frightening is that the baby will seem healthy and there will be no signs during pregnancy, all will seem well for the first few months. Patients with type I will usually show symptoms within six months of being born and children diagnosed with this type usually die before the age of two. Babies who suffer from type I will suffer from labored breathing, trouble feeding, swallowing, and even supporting their heads. In its later stages, affected children may suffer from respiratory infections and lung collapses. They will never sit or walk without help. The vast majority of SMA cases (at least 60 percent) are type I. Avery suffered from type I and her father wrote that she died after her lung collapsed and she went into cardiac arrest.
Is There a Cure?
SMA has no cure. Treatment is aimed at managing symptoms and revolves around nutrition, breathing, and exercise. Breathing is key because the muscles that stop working first are usually involved in breathing, and as a result children are more at risk for respiratory infections and pneumonia. Physical therapy is crucial in helping the baby with breathing, swallowing, and to exercise the joints, which can go bad from lack of use. As the baby’s health situation gets worse, they may need to additional aids like breathing machines or surgical procedures.
Even the mildest of colds can lead to a long hospital stay for a baby with type I SMA, and health-care costs “can put a big financial strain on family,” Hobby says. Between emergency-room runs, hospital visits, wheelchairs, and other equipment, costs can skyrocket. For a baby with type I, the costs may be in the hundreds of thousands. Even for a patient with one of the less-severe types, the price will be in the tens of thousands, and with a longer life expectancy, “it obviously stretches out,” Hobby explains.
At this point, Hobby explains, the treatment is “really all about managing the symptoms” rather than fixing the cause of the disorder. “There is no approved treatment or cure yet,” he explains. However, there may be better treatments and, possibly, even a cure on the horizon. Hobby says that researchers have made tremendous strides in the last ten years, since they have been able to identify precisely the SMN1 gene that causes SMA. The first clinical trial for a drug was approved last year. Currently, there are three new drugs in clinical trials and an additional ten programs are in the early stages of development. One possible drug would involve boosting the power of SMN2, a sort of backup gene that exists in the body, which has about 20% of the capacity of SMN1. People with less severe cases of SMA, have more copies of this backup gene. If scientists can boost SMN2 enough, then they may be able to overcome the absence of SMN1.
A cure is certainly a long way off. Even the approved clinical trials will take many years to complete. But at least now, researchers have direction. “There’s a lot of hope on the research side,” Hobby says. “We know what we’re doing, we just need to raise the money.”