Progressive muscular weakness in infants, referred to as Spinal Muscular Atrophy
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Spinal Muscular Atrophy (SMA) is a genetic disorder that affects the nerve cells in the spinal cord, leading to muscle weakness and impaired movement. Approximately 10,000-25,000 children and adults in the United States live with this condition [1].
In newborns and infants, the early signs and symptoms of SMA typically appear within the first 6 months of life. These may include:
- Muscle weakness and low muscle tone (floppiness): Infants may seem "floppy," with weakness in the shoulders, arms, legs, torso, and hips.
- Poor head control: Difficulty holding the head up.
- Reduced movement of the arms and legs: Affected infants may have limited movement in their limbs.
- Difficulty sucking, swallowing, or breathing: This can manifest as feeding problems.
- Weak cry or cough: Affected infants may have a weak cry or cough.
- Inability to sit or roll independently by 6 months: Affected infants may not be able to sit or roll independently.
- Tremors or muscle twitching may also occur.
- Less movement may be observed even before birth, and joint deformities can be present at birth in the most severe cases (Type 0 SMA).
Type 1 SMA, known as infantile-onset SMA, presents with these signs by 6 months or earlier and is characterized by generalized muscle weakness and failure to reach developmental milestones such as sitting unassisted [3].
SMA can increase the risk of infant death when doctors diagnose it in infants and children [2]. However, with early diagnosis and appropriate treatment, many individuals with SMA can lead fulfilling lives.
SMA is caused by changes, or mutations, in the SMN1 gene. Chorionic villus sampling and amniocentesis are tests that can be performed during pregnancy to find out whether an individual has the genetic change that may lead to SMA. Doctors can also take a blood sample to check for changes in the SMN1 gene [4].
There are different types of SMA, each with its own set of symptoms. Type 2 SMA symptoms appear when the child is 6-18 months old and may make it difficult for them to stand or walk, and they may have breathing difficulties. Type 3 SMA, or Kugelberg-Welander disease, develops after age 18 months and can cause difficulties in climbing stairs, getting up from a chair, and may lead to scoliosis and muscle shortening. People who develop SMA symptoms later on have a greater chance of a positive outlook [1][3].
Treatment options for SMA have improved significantly in recent years. Onasemnogene abeparvovec is a gene therapy drug for SMA that is available as a single dose and has been effective in improving the life expectancy of individuals with SMA type 1. The FDA has also approved Evrysdi for children with SMA aged 2 months or older, an oral medication that contains risdiplam [5]. Nusinersen is an injectable drug for newborns with SMA that slows the progression of the condition and reduces muscle weakness [5].
A supervised home-based resistance-training exercise program can benefit children with SMA by helping to improve muscle strength and motor function [6].
Organizations such as Cure SMA, SMA Foundation, TREAT-NMD, and Spinal Muscular Atrophy UK offer information and resources for parents and caregivers of children with SMA [1]. Pregnant people with a family history of SMA or who already have a child with the condition are advised to see a genetic counselor [7].
People with SMA should avoid contact with those who do not feel well, as infections can lead to complications. The National Institutes of Health (NIH) recommends newborn screening programs to diagnose SMA in infants within the first 48 hours after birth [8].
Evrysdi increases the production of the survival motor neuron (SMN) protein, which helps the motor neurons in the brain and spinal cord control movement [5]. This is a significant advancement in the treatment of SMA, as the survival motor neuron protein is crucial for the health of the motor neurons that control voluntary muscles necessary for movement and vital functions like breathing and swallowing.
References:
[1] SMA Foundation. (n.d.). About SMA. Retrieved from https://www.smafoundation.org/About-SMA/What-is-SMA.aspx
[2] Mayo Clinic. (2021, February 11). Spinal muscular atrophy (SMA). Retrieved from https://www.mayoclinic.org/diseases-conditions/spinal-muscular-atrophy/symptoms-causes/syc-20354051
[3] Muscular Dystrophy Association. (2021). Spinal Muscular Atrophy (SMA). Retrieved from https://www.mda.org/disease/spinal-muscular-atrophy
[4] National Human Genome Research Institute. (2021, March 11). Spinal muscular atrophy. Retrieved from https://www.genome.gov/genetics-health/disease-information/spinal-muscular-atrophy
[5] FDA. (2020, December 23). FDA approves Evrysdi (risdiplam) for the treatment of spinal muscular atrophy in pediatric and adult patients. Retrieved from https://www.fda.gov/news-events/press-announcements/fda-approves-evrysdi-risdiplam-treatment-spinal-muscular-atrophy-pediatric-and-adult-patients
[6] SMA Foundation. (n.d.). Exercise. Retrieved from https://www.smafoundation.org/Care-and-Support/Living-with-SMA/Exercise.aspx
[7] Mayo Clinic. (2021, February 11). Spinal muscular atrophy (SMA): Diagnosis and treatment. Retrieved from https://www.mayoclinic.org/diseases-conditions/spinal-muscular-atrophy/diagnosis-treatment/drc-20354057
[8] National Institutes of Health. (2021, March 11). Newborn Screening for Spinal Muscular Atrophy. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK544084/
- Spinal Muscular Atrophy (SMA) is a neurological disorder that falls under the category of chronic diseases, affecting the nerve cells in the spinal cord, and is a type of health-and-wellness issue that pediatricians often encounter in their practice.
- Newborn screening programs, technologies such as chorionic villus sampling and amniocentesis, and genetic counselors play crucial roles in the early detection and management of SMA, a medical condition that has neurological implications.
- Treatment for SMA has significantly advanced in recent years, with the approval of Evrysdi, an oral medication containing risdiplam, and gene therapy drugs like Onasemnogene abeparvovec, demonstrating the progress science has made in addressing neurological disorders like SMA.
- Support networks like Cure SMA, SMA Foundation, TREAT-NMD, and Spinal Muscular Atrophy UK offer valuable information and resources for parents and caregivers of children with SMA, helping them navigate this neurological-disorder-related challenge more effectively.
