CONDITIONS
Spinal Muscular Atrophy
An inherited (genetic) disease affecting the nerves and muscles, Spinal muscular atrophy (SMA) causes the muscles to become increasingly weak. In India, SMA is the second most common fatal autosomal recessive disorder, with a prevalence of 1 in 10,000 live births and a carrier frequency of approximately 1 in 50.
There are different types of SMA, but the seriousness depends on the type that the child has.
What are the symptoms of Spinal Muscular Atrophy?
Symptoms vary a lot, depending on the type of SMA:
Type 0: Rarest and most severe form of SMA and develops while a woman is pregnant. Symptoms are:
- Less movement of Babies in the womb
- Babies are born with –
- joint problems,
- weak muscle tone,
- weak muscles for breathing – Often survival is difficult due to breathing problems.
Type 1: Severe type of SMA and about 60% of people with SMA have type 1.
Symptoms are:
- A child is unable to support their head or sit without help.
- Floppy arms and legs
- Problems swallowing.
It is difficult for most children with type 1 SMA to survive past their second birthday.
Keeping in touch with the medical team, family members, and others is important for emotional support while the child fights this disease.
Type 2 (chronic infantile SMA): Affects children 6-18 months old. The symptoms range from moderate to severe and usually involve the legs more than the arms. The child may sit and walk or stand with help.
Type 3 (Kugelberg-Welander disease or juvenile SMA): Symptoms start around the age of 2-17 years old and is the mildest form of the disease. The child most likely able to stand or walk without help but may have problems running, climbing stairs, or getting up from a chair. They may need a wheelchair to get around later in life.
Type 4: Adult form of SMA. Symptoms are:
- Muscle weakness,
- Twitching, or breathing problems.
Usually, only the upper arms and legs are affected, and symptoms are present throughout life, but can be managed by continuous movement and exercised under a specialist such as a physical therapist.
What are the causes of Spinal Muscular Atrophy?
Spinal Muscular Atrophy is a disease that is genetic, meaning that it is passed down through families. A child gets SMA if they have two sets of a broken gene, one from each parent, because of which the body is unable to make a specific kind of protein. Without this protein, the cells that control muscles die. If the child gets only one gene from any of the parent, the child won’t get SMA but will become the carrier of the disease. This broken gene could be passed on to own child at a later stage.
How is Spinal Muscular Atrophy diagnosed?
Sometimes, SMA is hard to diagnose if the symptoms resemble those resulting from other conditions muscular dystrophy. To find the cause of symptoms, the doctor conducts a physical exam and a medical history. Some tests to diagnose SMA are:
- Blood test to check for enzyme and protein for high levels of creatine kinase that increase as a result of degrading muscles.
- Genetic test to identifies problems with the SMN1 gene.
- Nerve conduction test (electromyogram (EMG)) to measure the electrical activity of nerves muscles and nerves.
Muscle biopsy: Rarely, a physician may perform a muscle biopsy.
Can SMA be diagnosed during pregnancy?
In case of a family history of SMA, prenatal tests in pregnancy may determine if the developing fetus has the disease. Prenatal tests for SMA include:
Amniocentesis: This test takes place after the 14th week of pregnancy and checks for the fluid for SMA
Chorionic villus sampling (CVS): A small tissue sample from the placenta through the cervix or stomach is removed and the sample is checked for SMA. CVS may be conducted as early as the 10th week of pregnancy.
What are the treatment options for Spinal Muscular Atrophy?
There’s no cure, but treatments can improve some symptoms and, in some cases, help your child live longer.
There are three approved medications to treat SMA: nusinersen (Spinraza), onasemnogene abeparvovec-xioi (Zolgensma) and risdiplam (Evrysdi). These treatments are forms of gene therapy that affect the genes involved in SMA. The SMN1 and SMN2 genes give the body instructions for making a protein that helps with controlling muscle movement.
Besides gene therapy, the doctor suggests a few other ways to help manage symptoms:
- Breathing – With SMA, weak muscles keep air from moving easily in and out of the lungs and hence few breathing techniques help or for severe problems, the child may use a machine that helps them breathe.
- Swallowing and nutrition –Weak muscles in the mouth and throat make it difficult for babies with SMA to suck and swallow. In such cases, the doctor suggests working with a nutritionist and some babies may need a feeding tube.
- Movement – Physical and occupational therapy, which use exercises and regular daily activities to help protect the child’s joints and keep muscles strong.
Back issues – Children may get a curve in their spine once SMA starts. A doctor may suggest a back brace for the spine and surgery can fix the problem at an older age.
What is the outlook for people with SMA?
The quality of life and life expectancy for people with SMA varies depending on the type and severity. Infants with type 1 SMA usually die before their second birthday. Children with type 2 or type 3 SMA may live full lives depending on the severity of symptoms. People who develop SMA during adulthood (type 4) often remain active and enjoy a normal life expectancy.
Caring for a child with SMA:
- There’s a lot that could be done to help a child of SMA with some of the basic tasks of daily life.
- A team of doctors, therapists, and support groups may help with the child’s care and the child will probably need lifelong care from different types of doctors and specialists such as
- Pulmonologists (lungs)
- Neurologists (nerve problems)
- Orthopedists (bone problems)
- Gastroenterologists (stomach disorders)
- Nutritionists
- Physical therapists (exercise specialist to improve child’s motion)
The important thing while caring for the child is not get overwhelmed by the task of managing care and take help of the specialists to manage the disease.
- Check for support groups to share experiences with others and learn from others.
- One such support group is Cure SMA Foundation of India.
Cure SMA Foundation of India is a parent-led community initiative, Cure SMA Foundation of India aims to raise awareness about SMA, build infrastructure for better management of the disease, and advocate for broader access to available and approved treatments and clinical trials.
References
- Kesari, A., Rennert, H., Leonard, D.G. et al.SMN1dosage analysis in spinal muscular atrophy from India. BMC Med Genet 6, 22 (2005)..
- Spinal Muscular Atrophy. Cleveland Clinic. March 2024. https://my.clevelandclinic.org/health/diseases/14505-spinal-muscular-atrophy-sma
- Spinal Muscular Atrophy. WebMD. May 2024. https://www.webmd.com/brain/spinal-muscular-atrophy
