Floppy limbs, weak coughs: Key warning signs of spinal muscular atrophy in babies

In their first year of life, a baby typically learns to lift his head, roll over, crawl and perhaps even take his or her first steps. But for infants with spinal muscular atrophy (SMA), these seemingly simple movements can be monumental challenges. 

This rare genetic condition, which affects one in 10,000 births globally, can dramatically alter the course of a child’s development.

The first signs can be subtle – a baby appearing unusually “floppy”, breathing rapidly, having difficulty sucking or swallowing, or having frequent and prolonged coughs.

“SMA is a rare genetic disease that results in progressive muscle weakness and paralysis,” says Dr Wendy Liew, a paediatrician and child neurologist at Dr Wendy Liew Paediatric and Child Neurology Centre. 

The condition, she adds, occurs when there is a lack of the survival motor neuron gene, called the SMN1 gene, leading to insufficient production of the crucial proteins that are needed for motor neurons – the nerve cells that control our muscles. Without this protein, motor neurons are irreversibly lost and this results in muscle weakness. 

According to Dr Liew, there are four types of SMA that could potentially develop from birth, all the way to young adulthood. 

“In Types 1 and 2 SMA, affected children often present with motor developmental delays during infancy,” she says. “In older children with the milder variant of SMA, many are capable of standing and walking, but may encounter differing severity of motor difficulties, such as frequent falls. Type 4 SMA, the least severe form of SMA, usually develops in young adulthood.”

SMA typically occurs when both parents carry a non-functional copy of the SMN1 gene. If both parents are carriers, their baby has a 25 per cent chance of developing SMA. But because carriers usually show no signs of SMA, coupled with the fact that testing for SMA is currently not part of the routine newborn screening process, there is often little awareness for the disease, leading to delays in diagnosis and management.

Dr Liew adds that the younger the child is when symptoms first manifest, the more severe the disease tends to be. Early detection is critical, as it can lead to early diagnosis, intervention, as well as access to treatment options which aim to help preserve motor neurons and motor function. 

“This is why it is pertinent that parents follow the timelines of the routine developmental screening as recommended by MOH,” says Dr Liew. “This is when doctors can identify the children who are at risk of developmental delay.”

Once SMA is detected, supportive care from a multidisciplinary team will play a critical role in helping a child manage their symptoms. 

These include physiotherapy, occupational therapy and speech therapy, which can strengthen muscles, correct or improve sitting and standing postures. Coupled with medical treatment, these therapies can also prevent complications such as joint contractures – which occur when muscles, tendons, skin, and nearby soft tissues shorten, leading to functional limitations.

At the same time, parents should also consider the psychological impact a child’s SMA diagnosis can have on the rest of the family. Dr Liew notes that families affected by SMA often experience high levels of emotional stress due to having a child with a disability and the uncertainty of his or her future. Financial strain from the increased medical demands adds to this stress. Siblings may also be affected psychologically as parents may spend more time and attention on the affected child due to his or her medical needs. 

According to a study conducted jointly by the National University of Singapore, National University Hospital, KK Women’s and Children’s Hospital and Novartis Singapore to investigate the economic burden of SMA in Singapore, 64 per cent of mothers have either left the workforce or switched from full-time to part-time work to accommodate caregiving duties. This income loss, together with the long-term, direct costs of having to care for a child with SMA and going for regular hospital appointments, means there is a high economic burden on families. 

Dr Wang Yi, a health economist from Saw Swee Hock School of Public Health and one of the researchers of the study, adds: “Caregivers also often experience chronic pain from back injuries, as a result of repeatedly lifting and moving SMA patients. Many face a decline in their overall physical health because they have little time to maintain a regular lifestyle.”

Dr Wang emphasises the need for comprehensive support for SMA patients and their families. While current policies such as the Tripartite Standards includes Flexible Work Arrangements and Unpaid Leave for Unexpected Care Needs exist, more support is required to keep mothers in the workforce and aid their re-entry. 

“It's important to consider the broader societal impact when developing effective interventions and support systems.” he adds. “Regular mental health screenings are crucial to ensure caregivers receive the psychosocial support they need, while community support can increase their access to leisure activities and a social life.” 

The study’s findings provide a foundation for ongoing discussions on healthcare policies shaping interventions for managing SMA. These insights aim to foster a more comprehensive approach to handling rare diseases with significant economic impact such as SMA. 

For now, support is available through medical social workers and non-profit organisations.

Says Dr Liew: “Organisations such as the Muscular Dystrophy Association Singapore or Rare Disorders Society Singapore help to provide both care and psychosocial support to these families. Through these, they meet other family members with children who are affected with the same disease.”

Medical experts emphasise that parents should also be aware of SMA and its symptoms, and seek medical advice if they notice any developmental concerns in their child. 

Dr Liew says early detection and management of SMA has changed the characteristics of SMA patients, hence improving their quality of life. For example, with the current available treatments, some children with Types 1 and 2 SMA have been able to achieve developmental motor milestones which were previously deemed not possible. 

“Every child with SMA is different, and discussing the appropriate care and disease management with the family and the multidisciplinary team can help the child have a better quality of life,” she adds.