Asthma isn’t always a quick and easy diagnosis in children. According to a 2014 task force assembled by the American Thoracic Society and the European Respiratory Society, pediatric severe asthma can be diagnosed if a child’s symptoms require treatment with high-dose inhaled corticosteroids plus a second “controller” medication for a full year, and/or systemic corticosteroids for half a year or longer. In other words, its diagnostic criteria are based on the intractability of its symptoms.
“It’s definitely a limitation when you’re defining a disease state based on how much medicine is needed to control it, but part of that is because asthma is such a heterogenous disease,” says Dr. Jonathan Gaffin, co-director of the severe asthma program at Boston Children’s Hospital and an assistant professor of pediatrics at Harvard Medical School.
In some children with severe asthma, the condition causes daily breathing problems but few outsize exacerbations. In others, this trend is reversed; extended periods of symptom-free living are broken up by infrequent but serious flares. In fact, a young person’s lung function may appear normal and healthy in between exacerbations, which experts say is one difference between severe asthma in children as opposed to severe asthma in adults.
Severe asthma has another defining trait: it tends to show up very early in life. “By the time they walk through the school gate for the first time, they already have permanently impaired lung function and, in most, symptoms are there,” says Dr. Andrew Bush, an asthma specialist and director of the Imperial College London Centre for Paediatrics and Child Health. He says that in some cases, the asthma may only become severe and unmanageable later in childhood. But it’s exceedingly rare for a child with no signs of asthma to develop the condition beyond the first years of life. “There are cases that appear to be later onset, but if you look back, you find most had symptoms they forgot about as younger children,” Bush explains.
While severe asthma in kids is defined by its resistance to treatment, there are some newer medications that can bring the condition under control and prevent the need for systemic corticosteroids or other aggressive remedies, which may be especially risky for growing and developing kids. However, experts say that long before those medications are deployed, important diagnostic work must be done to reveal if a child’s asthma truly is severe.
Uncertain prevalence
Asthma is one of the most common medical conditions in young people. By some estimates, almost 1 in 10 American children under the age of 15—which equates to nearly 6 million—has asthma. Experts agree that rates of asthma in children have risen dramatically during the past 40 years (although there’s evidence that this increase has slowed considerably in recent years).
When it comes to severe asthma in children, there’s more room for disagreement. While some estimates peg its prevalence, roughly, at between 2% and 5% of all pediatric asthma cases, experts say it’s hard to know for certain. That’s because many kids with hard-to-control symptoms may be struggling due to poor medication adherence, regular contact with allergens, or other factors. “More than half of the children referred to me with possible severe asthma in fact have a problem with environmental exposures or with how they’re using their inhaler—that sort of thing,” Bush says. These situations are sometimes termed “difficult to treat” asthma.
In other cases, a child’s breathing problems may turn out to be the result of non-asthma conditions, which explains why the medications aren’t helping. For example, inducible laryngeal obstruction is a reversible and temporary narrowing of the larynx that can mimic the symptoms of asthma. Chronic infections can also cause asthma-like symptoms. To diagnose severe asthma, those must be ruled out.
While the exact prevalence of severe childhood asthma is hard to nail down, experts agree that the condition is responsible for a large share of asthma-care expenditures. According to a 2017 study in the Journal of Allergy and Clinical Immunology, of the $10 billion spent every year on childhood asthma in the U.S., as much as half of that money is used to treat kids with severe asthma, whether for hospitalizations, medications, or in-office visits.
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Causes, presentation, and diagnosis
Why do children develop severe asthma? The usual suspects—environmental exposures combined with a genetic susceptibility—are a safe bet. But elucidating the specific causes of severe asthma is challenging. “The pathogenesis of asthma is really complex in children, and many mechanisms may be responsible,” says Dr. Marielle Pijnenburg, head of the department of pediatric respiratory medicine and allergology at Erasmus University Medical Center in the Netherlands.
Pijnenburg says that allergic triggers, viral infections, diet, air pollution, tobacco smoke, and microbiome disturbances are all being looked at as possible contributing factors. But filling in the existing knowledge gaps will be difficult. “To look into the lungs and see what’s going on requires invasive tests that are not feasible in children,” she says.
When it comes to the disease’s presentation, for many kids, the very first symptoms appear quite early in life—by age 1 or 2. “The child has a viral cold and develops a wheeze, or often has severe attacks of wheeze,” Bush says. Among those kids who will go on to have severe asthma, he says that several factors predict this progression: in-home exposure to tobacco smoke before the age of 3, sensitivity to multiple allergens, and severe wheezing attacks that require hospitalization.
While the first symptoms usually begin at a very young age, it can be difficult to assess lung function or other asthma-related diagnostic criteria in small children. And so in most cases, it’s hard to know if severe asthma is present until children are school aged—at least 5 or 6 years old.
Again, this diagnosis requires a lot of process-of-elimination work. It is becoming increasingly common for a young person’s care team to perform an in-home evaluation. “Someone goes to the home of the child to see if there are dust mites or mold or pets, or if one of the parents smokes,” Pijnenburg explains. She says that one of the things that differentiates childhood severe asthma from severe asthma in adults is the commonness of allergic triggers. While about half of adults with severe asthma have allergies that make the condition worse, this rises to 80-85% of kids with severe asthma. Identifying and attempting to remove allergic triggers is a crucial step.
It’s also becoming common for kids with symptoms of severe asthma to receive an evaluation from a multidisciplinary care team that includes a pulmonologist, but also an allergist and even a mental health counselor or specialist. “Kids with asthma can experience scary episodes where they are really having trouble breathing, and by the time we see them, they’ve been admitted to the hospital or ICU, and they’ve experienced a lot of poking and prodding that can lead to anxiety,” Gaffin says. This anxiety can cause distress, which can make asthma symptoms worse and also harder to manage.
Once these contributing or exacerbating factors have been assessed and ideally resolved, and assuming other tests confirm the presence of asthma, a diagnosis of severe asthma is warranted if a young person continues to experience severe symptoms or flares.
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How severe asthma is treated
Asthma specialists talk a lot about “getting the basics right.” That means long before the newest and most-aggressive class of drugs are considered, it’s essential to ensure that young people are taking their medications properly.
“Medication adherence is probably the biggest issue,” Gaffin says. Again, a lot of kids with severe asthma feel pretty good between flares, which can cause them to neglect their inhalers or other meds. “But even children with severe asthma who [have]symptoms have difficulty taking their medications as prescribed on a regular basis,” Gaffin says. “Are they holding their breath after inhaled corticosteroids for 10 seconds to make sure the medicine gets deep into the lungs?” These are the types of lapses that he sees in both kids and in adults with severe asthma. In some cases, fixing these issues can bring the asthma under control.
Once medication lapses and all other modifiable triggers have been dealt with, kids with severe asthma may be eligible for a “biologic” drug, so named because it is derived from a living organism. For severe asthma, all of the biologic therapies are monoclonal antibodies—specialized proteins that affect the function of the immune system in ways that mitigate the kind of inflammation that drives asthma symptomology. The U.S. Food and Drug Administration has approved three of these drugs for use in children with severe asthma, and all three are given via skin injection, typically at the doctor’s office. Sometimes doctors will observe kids for up to two hours after administering an injection. “Usually they’re given every two or four or eight weeks, and they tend to be very effective,” Gaffin says. In most cases, kids on these drugs experience fewer severe flares and daily symptoms.
But there are potential drawbacks to these drugs, including pain from the injections, headache, sore throat, fatigue, and a risk for allergic reactions. The potential long-term effects of the drugs are also unknown. “One of the issues is that even though these drugs are tested, there usually aren’t as many pediatric participants in clinical trials, so a lot of the data is extrapolated from adults,” Gaffin says.
Bush puts it more bluntly. “It’s a scandal that almost all the data are in children 12 and older and adults,” he says. “Younger children are a forgotten population.” He agrees that biologics often work well, and he prescribes them when appropriate. “But they are hardcore expensive, and nobody knows the optimal duration of treatment,” he adds.
Severe asthma, unlike asthma that is milder and more manageable, tends not to resolve or improve as a child matures into adulthood. However, Bush says the disease does change, and it’s hard to know based on the current available evidence whether biologics are needed indefinitely, or whether temporary courses could be effective.
Pijnenburg reiterates many of these concerns, but also emphasizes that biologics can be “life changers” for some kids. “We don’t know if we need to continue them forever, or if we can wean kids off them, or how we should wean them,” she says. “But we often get excellent control with biologics, so kids go into adulthood with not too many symptoms.”
While severe asthma is a complex and hard-to-manage condition in children, the newest medications—coupled with a more rigorous approach to identifying environmental and lifestyle factors that may contribute to a child’s symptoms—is helping more kids find relief from their asthma. That kind of progress is worth celebrating.
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