Children with SMA face higher risk of severe RSV, study finds

Children with spinal muscular atrophy (SMA) have a higher risk than their peers in the general population of developing severe respiratory syncytial virus (RSV) infections, a nationwide study from Taiwan found.

SMA kids were more likely to be hospitalized, require admission to an intensive care unit (ICU), and use ventilatory support for breathing, the study showed. The mean age of RSV infections in SMA patients was past the second birthday, and  ICU admissions became more common as children got older.

“These findings underscore the significant respiratory vulnerability of patients with SMA, particularly within pediatric populations, and highlight the urgent need for targeted preventive strategies for children over two years old,” the researchers wrote.

The study, ”Burden of respiratory syncytial virus in spinal muscular atrophy: a retrospective nationwide cross-sectional and birth cohort study,” was published in Orphanet Journal of Rare Diseases.

Respiratory complications are the chief cause of death in SMA. Patients with this rare genetic disease primarily experience weakness of the muscles involved in breathing out, resulting in impaired airway clearance and susceptibility to lower respiratory tract infections.

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Common virus

One such infection is caused by RSV, a common respiratory virus. Severe RSV infections are more common in infants and in children with conditions such as congenital heart disease or genetic disorders.

However, little data are available about how RSV affects people with SMA specifically.

“Considering the recent breakthroughs in SMA treatment that have significantly improved the lifespan and quality of life for patients with SMA, it is essential for individuals with SMA and their families to proactively plan strategies to prevent RSV-related emergencies,” the researchers wrote.

They assessed the relationship between SMA and RSV risk using a Taiwanese health insurance database. Through claims data, they found 914 people with SMA (age range 0-70) who were hospitalized from 2009 to 2021.

Disease-modifying treatments for SMA became available in Taiwan in 2020. “Our findings therefore primarily reflect the burden of RSV infection in patients with SMA during the pre-treatment era,” the team noted.

Across 914 hospitalizations, 14 (1.5%) were related to RSV, and 46 (5%) were lower respiratory tract infections more broadly. Unlike lower respiratory tract infections, RSV hospitalizations only affected people younger than 18.

SMA patients hospitalized with RSV were more likely to need respiratory support or require treatment in an ICU than those caused by lower respiratory tract infections. However, these differences didn’t reach statistical significance.

To be able to make analyses using a more comparable age range, the team identified a birth cohort of 110 people with SMA born from 2009 to 2020. They examined the medical histories of this group through 2021, comparing them with those of more than 2 million children born without SMA during the same period.

In the birth cohort, significantly more people with SMA were hospitalized with RSV (9.8%) than people without SMA (1.6%). On average, SMA patients were also significantly older at the time of RSV hospitalization (2.54 vs. 1.05).

ICU admissions (54.5% vs. 4.7%) and ventilation rates (54.5% vs. 1.7%) were significantly higher for SMA children than non-SMA children.

“Given that patients with SMA, particularly those with earlier onset, may already require long-term ventilatory [breathing] support, the reported ventilator use rates may partly reflect baseline respiratory status,” the team noted.

ICU admissions increased as the patients got older, the study found, rising from 25% in children younger than 1 to 100% in those aged 4 or older. “This trend aligns with the progressive nature of SMA, as older children may experience declining respiratory muscle function, increasing their risk for a more severe clinical course and pulmonary compromise with RSV or other respiratory viruses,” the investigators wrote.

The scientists said the results may help inform the development of RSV prevention strategies for people with SMA. Monoclonal antibody therapy is a preventive RSV treatment, but it is indicated primarily for infants younger than 2.

“Future research into the efficacy of RSV monoclonal antibody therapies in children over two years old is crucial for optimizing patient outcomes and healthcare resource allocation, particularly during critical developmental stages and seasonal peaks,” the team wrote.

Among the study’s limitations, the scientists noted that using claims data precluded them from comparing patients with different SMA types and accurately determining the precise age of symptom onset.