January 21, 2022

Article at SpineUniverse

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SMA Types 2 and 3: What You Need to Know

As a new parent, your life looks nothing like it used to. While you’re suddenly flooded with love for a tiny human, you’re also managing sleep deprivation while caring for someone who can’t tell you what they need. (Cue lots of crying.)

For parents of children with spinal muscular atrophy (SMA), the stress of parenting increases exponentially. SMA is a rare genetic condition which, if untreated, causes weakness, respiratory problems, immobility, and in some cases, can be fatal.

Man with SMA type 2 or 3 using wheelchair
New therapies are giving people with SMA types 2 and 3 massive quality of life boosts.

If your child has SMA type 2 or 3, you’re probably wondering if their life will look anything like the one you envisioned. However, early screening and new cutting-edge medicines mean many babies and children with SMA can live long, healthy lives with minimal, if any, special needs. And if you catch the diagnosis later in life, those new medications make it possible to stop the disease from progressing.

SMA happens when you’re born without a functional SMN1 gene. As a congenital condition—something you’re born with—it’s not something you could have prevented. The SMN1 gene makes a protein that’s vital for communication between your muscles and your nerves. Without it, you may have difficulty performing basic functions, including everything from breathing to walking.

When the SMN1 gene isn’t working or is absent, your body relies on another gene, SMN2, to manufacture that protein. And while the SMN2 gene certainly helps, it produces “a backup, but imperfect protein,” says Mark Fisher, MD, a pediatric physiatrist at Mercy Children’s Hospital in Kansas City, Mo. Bottom line: SMN2 isn’t fully equipped to fill in for SMN1.

The disease is characterized by proximal (meaning near the torso) weakness that’s more pronounced in your lower body than your upper body. Without treatment, SMA inevitably leads to progressive motor (muscle) weakness, including your legs, arms, and in severe cases, your respiratory muscles, which is why it can be fatal.

The severity of your symptoms, explains Dr. Fisher, depends on how many copies of the SMN2 gene you’re born with. Generally, SMA 2 shows up in people with three copies of SMN2, while people with SMA 3 have three to four copies of SMN2.

Types of SMA

There are five types of SMA.

  • SMA Type 0 is present in utero and usually lead to miscarriage or death by six months of age. Newborns with SMA type 0 generally demonstrate abnormal breathing, swallowing problems, respiratory failure, profound weakness, and abnormal joints. Babies with SMA 0 never roll over or sit up on their own.
  • SMA Type 1 is diagnosed before the six-month mark. Symptoms, which include low muscle tone, limited movement, and problems with swallowing, feeding, and breathing, get worse over time. Untreated, SMA Type 1 often leads to fatal respiratory failure by age two; few children with SMA 1 live beyond age four.
  • SMA Type 2 tends to be diagnosed between six and 18 months of age. They also experience difficulty with mobility and breathing, although not to the same extent as children with SMA 1. Without treatment, the course of the disease varies, but people with SMA 2 generally require wheelchairs for mobility and their life expectancy is typically early 20’s.
  • SMA Type 3 occurs in children who are at least 18 months old, with the first sign typically being leg weakness. Children with SMA 3 can sit, stand, and walk independently however the hallmark signs include difficulties with activities such as running, climbing stairs, or standing up from a seated position. With treatment, SMA 3 generally doesn’t impact your lifespan.
  • SMA Type 4 is an adult-onset form of the disease, presenting after age 21. Cases vary in severity, however most people SMA 4 maintain the ability to walk albeit slowly and with increasingly limited endurance over time. As with all forms of the disease, treatment won’t reverse muscle atrophy that has already occurred, but it can prevent further decline.

SMA 2 Symptoms

SMA Type 2 is typically diagnosed between six and 18 months old, although according to Dr. Fisher it can be diagnosed in children up to two years old.

While babies with Type 2 SMA may meet some of their developmental milestones, they’re often delayed. As with all types of SMA, type 2 is characterized by weakness that affects the lower body more significantly than the upper body.

Babies with SMA 2 can usually sit up by themselves but may need help getting into a sitting position on their own, says. Dr. Fisher. Without treatment, most people with SMA 2 lose that ability by the time they reach their mid-teens.

While physical and occupational therapies are helpful in maximizing their abilities, people with SMA 2 require assistance to stand and walk and can lose their ability to safely swallow over time. They may need a feeding tube and/or respiratory support such as the use of a BiPAP (bidirectional positive air pressure) machine. According to Dr. Fisher, most people with SMA 2 rely on a power wheelchair for mobility.

Other hallmark signs of SMA 2 include finger tremors, as well as musculoskeletal issues such as scoliosis, hip dislocation, and joint contractures. Joint contractures occur when the muscles, tendons, or other tissues around the joint shorten, thereby limiting range of motion.

Until very recently, people with SMA 2 relied on occupational and physical therapy to maximize their function and were generally expected to live into their late 20’s. Today early detection and innovative new treatments are making a world of difference; if you start early enough, groundbreaking medicines can keep SMA from affecting your daily life.

SMA 3 Symptoms

SMA 3 is generally diagnosed between 12 to 18 months of age (after your baby starts walking) through adolescence. Like type 2, it’s characterized by breathing difficulties and muscle weakness, and while they may hit their milestones later than their peers, most children with SMA 3 are able to sit and stand on their own. According to Dr. Fisher, most adopt a distinct gait pattern, have trouble running, and eventually lose the ability to walk. Most people with SMA 3 will eventually require a wheelchair.

Baby with SMA type 3 sits up
Most children with SMA type 3 will be able to sit up on their own.

Some experts divide people with SMA 3 into two subsets; SMA3a includes people who experience the onset of symptoms before age three, while SMA3b includes those who developed symptoms after age three. Depending on whether you fall into the category of SMA3a or SMA3b, you’ll typically maintain the ability to walk into your 30s or 40s, respectively.

Typically, with rehabilitation, people with SMA 3 make functional gains through the age of six, at which point they begin to decline. That decline often sharpens in adolescence. According to Dr. Fisher, this steep drop-off doesn’t necessarily mean the disease process is speeding up. Rather, it simply becomes harder for your muscles to keep up with the increasing demands of your limbs as you experience periods of rapid growth.

Because the disease primarily affects the proximal lower extremities (upper legs and hip muscles), spreading to the shoulders and arms over time, SMA 3 typically makes it difficult to walk, run, and climb stairs. Those issues, plus the general fatigue which is common among those with SMA 3, can seriously impact your quality of life. Frequently, the condition also causes finger trembling, scoliosis, and the absence of the patellar reflex (when you kick after the doctor taps your knee with the rubber mallet).

Until recently, people with SMA 3 needed regular physical and occupational therapy to maximize their functional capacity. While rehabilitation can still be an important part of treatment, in the past few years, exciting new drug therapies have completely changed the game for people living with SMA 3, particularly those in whom it is detected early.

Getting a diagnosis used to involve a variety of measures, including muscle biopsy and EMG nerve conduction studies. Today, that’s no longer the case, says Dr. Fisher. In many cases the diagnostic process begins before any symptoms are apparent, regardless of what type of SMA is present.

In 2018, SMA was added to the federal Recommended Uniform Screening Panel (RUSP), the list of suggested conditions to include in statewide universal newborn screening programs. Since then, early detection has helped thousands of children avoid irreversible losses. As of January 2022, 39 states include SMA in routine newborn screens — which means 86 percent of babies are now screened at birth.

Baby being checked for SMA types 2 and 3 with heel prick
SMA was added to the RUSP (the heel prick) in 2018; now, about 86% of babies are screened for SMA at birth.

Once the screen picks up SMA, the next step is genetic testing. “It’s much faster than it used to be,” says Dr. Fisher. Not only does genetic testing provide conclusive results, it detects how many copies of the SMN2 gene are present, he says. If your child has SMA, your pediatrician should refer you to a local or regional treatment center where a specialist will help you determine the best course of treatment.

According to Dr. Fisher, “supportive care measures were basically the hallmark of care until the end of 2016.” Those measures included regular follow-up with physical and occupational therapists who would provide adaptive equipment, mobility aids, and home exercise programs with the goal of optimizing your child’s functional abilities, stamina, and overall quality of life. But the fact remains that SMA is a progressive, lifelong disease.

Thankfully though, there is now medication that can bring the disease process to a grinding halt. In December 2016, nusinersen (Spinraza) became the first ever FDA-approved SMA drug. Since then, two more groundbreaking medications, risdiplam (Evrysdi) and gene therapy (Zolgensma), have been FDA approved. All three can slow down or possibly even stop the disease process.

While the medications don’t promise to reverse the damage that’s already been done, they can prevent the disease from progressing further. While nusinersen and risdiplam are approved for use for anyone who is at least two months old, gene therapy hasn’t been approved for use in those older than two years. (According to Dr. Fisher, clinical trials testing gene therapy’s efficacy in older patients are currently underway.)

According to Dr. Fisher, there’s no simple answer to the question of which SMA drug to take. Age rules gene therapy out, but the decision about nusinersen or risdiplam must be made on a case-by-case basis, in collaboration with your health care providers. While clinical trials have proven the effectiveness of all three, Dr. Fisher says the studies didn’t measure the same outcomes, which makes direct comparison impossible. Furthermore, he says most of the studies have focused on the more severe SMA type 1.

While all the new SMA medical treatments are considered generally safe, given their novelty, there’s no way of knowing the long-term side effects. But, adds Dr. Fisher, more data becomes available every year. He says the medical community doesn’t expect any long-lasting side effects.

Nusinersen (Spinraza) According to Dr. Fisher, nusinersen “basically amplifies the protein made by SMN2” and is approved for anyone ages two months old and up (including adults). It’s delivered via spinal tap, or lumbar puncture. After receiving the first four “loading doses” during your first two months of treatment, you’ll need an injection every four months for the rest of your life.

While Dr. Fisher says the medication itself presents very few risks, the lifelong need for lumbar punctures is a drawback. In addition to the inconvenience factor, there are sometimes procedural difficulties. He says the most common side effect is a spinal headache that can be caused by cerebrospinal fluid pressure changes.

A 2019 study found that nusinersen ’s most common side effects were respiratory tract infections and constipation. Other issues included breathing difficulties, pneumonia, and increased needs for respiratory support.

Risdiplam (Evrysdi) Like nusinersen , risdiplam is also approved for those two months old and up and works to boost the SMN2 gene’s ability to produce SMN protein. Unlike nusinersen , risdiplam, which gained FDA approval in August 2020, is taken by mouth. It must be taken daily for the rest of your life and it must be refrigerated.

A 2020 study found that although it was generally well-tolerated, the most common side effects of risdiplam for those with SMA types 2 and 3 were fever, diarrhea, rash, canker sores, joint stiffness, and urinary tract infections.

Gene therapy (Zolgensma) Approved in May 2019 for patients under two years old, gene therapy is administered by a one-time IV injection designed to last a lifetime. New copies of functional SMN1 genes are injected directly into the bloodstream, where they instruct your body to make SMN protein.

According to Dr. Fisher, while gene therapy is generally safe, the main risk is possible liver inflammation. He says that most patients take a brief course of steroids to reduce that inflammation, weaning off it within a few months.

SMA’s impact on your life depends on how early you begin drug treatment. And with SMA screening increasingly being included in newborn screening panels, according to Dr. Fisher, some babies begin treatment as early as the first month or two of life,

With early treatment, children grow up needing nothing more than periodic neurology visits to monitor their progress, says Dr. Fisher. “[For] the young kiddos that we have that have received Zolgensma, there's nothing to work on.”

On the other hand, because the first SMA medication was only approved in 2016, many people with SMA didn’t have the opportunity to receive medication when they were younger and now live with chronic disabilities. According to Dr. Fisher, people with SMA types 2 and 3 require a team approach to their medical care and rehabilitation.

“Individuals with SMA types 2 and 3 will need regular visits with a neuromuscular specialist,” says Dr. Fisher. Typically, other important members of the team will be pulmonology, orthopedics, physical/occupational therapists, and nutritionists. They can expect to have braces for the feet or wrists and possibly a spine orthosis if they have scoliosis.”

For those with SMA 2, who never develop the ability to walk, and for those with SMA 3 who often lose that ability over time, a wheelchair is necessary for mobility. According to Dr. Fisher, you or your child may also need adaptive equipment to make activities like standing, toileting, and bathing safer and easier.

While we don’t expect to see significant improvements in older children who take medications like nusinersen and risdiplam, Dr. Fisher says many experience subtle strength gains when they start medication. Those gains might look like easier reaching, less fatigue with getting dressed, or simply the ability to operate the wheelchair controller with less effort. These improvements aren’t dramatic, but they certainly enhance quality of life.

Physical and occupational therapy will be an important part of the care team, although the extent of their involvement will depend on how early you receive medication and whether you have SMA 2 or 3. Rehab professionals will not only recommend the right adaptive equipment and train you and your caregivers in how to use it, they’ll also give you exercises to maximize your muscular strength and flexibility. This is of particular relevance, given the fact that people with SMA types 2 and 3 often experience musculoskeletal problems including scoliosis, joint contractures, and hip dysplasia (or hip dislocation).

Also, says Dr. Fisher, “It is important for parents and these patients to know that physical exercise is also helpful for minimizing weakness.” Although this can happen in the context of pediatric therapies, fitness programs can also be key as you or your child gets older.

If you have access to an adaptive sports program, take advantage of it. Dr. Fisher, who founded and directs the Children’s Mercy - Kansas City Adaptive Sports Medicine Clinic, suggests exploring Move United to see what’s available in your area.

Sports offer so much more than just physical benefits, regardless of your functional capacity. “Adaptive sports and recreation are incredibly valuable social integration, physical activity, and play,” says Dr. Fisher. “Even if a child uses a power wheelchair, sports like power wheelchair soccer or bocce can be fantastic ways for children to engage with their peers, make friends, and even fuel a competitive spirit. Participation and inclusion reverse the negative impact disability can have on mental health, builds self-confidence, and maximizes function.”

While SMA doesn’t affect cognition, many children with SMA 2 and 3 have a paraprofessional to assist with their care at school, says Dr. Fisher. And while some families may seek additional care assistance, including respite care at home, most will not need skilled nursing care. If you need help navigating the issues you or your child face, Dr. Fisher suggests consulting Cure SMA’s website. It’s “a fantastic resource for families that provides medical, treatment, research, and support resources.”

Whether your child just got an SMA diagnosis or you’re an adult who’s been living with SMA 2 or 3 for years, these new drug therapies may be able to alter the course of your disease — and your life. It’s never too late to explore treatment options. The earlier you begin, the more function you can preserve.