What is SMA?
Spinal Muscular Atrophy (SMA) is a serious neuromuscular disease caused by a genetic defect. It leads to the gradual weakening and wasting of muscles throughout the body, especially those responsible for movement, breathing, and swallowing.
SMA can appear at any age, from infancy to adulthood. However, symptoms in children are often more severe and appear earlier, significantly affecting growth, development, and quality of life.
Cause and Disease Mechanism
The primary cause of SMA is a mutation or deletion of the SMN1 gene (Survival Motor Neuron 1). This defect results in insufficient production of the SMN protein, which is vital for the survival of motor neurons in the spinal cord and brainstem.
Without enough SMN protein, motor neurons gradually degenerate. As a result, the muscles they control lose function, leading to muscle atrophy and progressive weakness.
Genetic Inheritance
SMA is inherited in an autosomal recessive pattern.
- A child develops SMA only if both parents carry the defective gene.
- If both parents are carriers, each pregnancy carries a 25% chance that the child will have SMA.
Many countries now provide carrier screening and newborn screening, allowing early diagnosis and treatment before symptoms appear.
Types and Severity of SMA
SMA is classified into four main types, depending on age of onset and disease severity:
1. SMA Type 1 – Werdnig-Hoffmann Disease
- Onset: Birth to 6 months
- Severe muscle weakness, poor movement, shallow breathing, difficulty swallowing
- Children cannot sit independently
- Most severe type; without treatment, life expectancy is shortened
2. SMA Type 2
- Onset: 6–18 months
- Children can sit but cannot stand or walk independently
- Risk of scoliosis and respiratory complications as they grow
3. SMA Type 3 – Kugelberg-Welander Disease
- Onset: After 18 months to early adulthood
- Children may walk initially but often lose this ability later in life
- Milder progression compared to Type 1 and 2
4. SMA Type 4
- Onset: Adulthood
- Slow progression, less impact on breathing and overall function
Symptoms in Children
- Weakness of arms, legs, and trunk muscles → delayed motor milestones (rolling, crawling, head control)
- Floppy or “frog-like” posture in infants with severe disease
- Shallow or rapid breathing, use of chest muscles to breathe
- Difficulty swallowing, poor feeding, frequent choking
- Complications such as scoliosis, joint stiffness, or joint dislocation due to muscle imbalance
Diagnosis
Diagnosis involves a combination of:
- History and physical examination – assessing muscle strength and developmental milestones.
- Genetic testing – to confirm mutation/deletion of the SMN1 gene.
- Electromyography (EMG) and nerve conduction studies – to evaluate nerve and muscle function.
- MRI (in selected cases) – to rule out other neurological conditions.
Treatment Approaches
Recent advances in therapy have transformed SMA care, improving both survival and quality of life.
- Disease-Modifying Therapies
- Nusinersen (Spinraza): Intrathecal injection that enhances SMN protein production from the SMN2 gene.
- Onasemnogene abeparvovec (Zolgensma): One-time gene therapy to replace the missing SMN1 gene.
- Risdiplam (Evrysdi): Oral medication that increases SMN protein production from SMN2.
- Supportive Care
- Physical therapy and rehabilitation medicine
- Non-invasive ventilation or cough-assist devices to support breathing
- Nutritional support and swallowing therapy
- Surgical Care
- Corrective surgery for scoliosis or severe orthopedic complications when necessary
Comprehensive SMA Care at Phyathai 2 Hospital
At Phyathai 2 Hospital, we provide specialized and multidisciplinary care for children with SMA. Our team includes pediatric neurologists, rehabilitation physicians, physiotherapists, nutritionists, and experienced nurses who work closely together.
This integrated approach ensures:
- Accurate diagnosis
- Personalized treatment planning
- Continuous monitoring of growth and development
- Holistic support for both the child and family
Our goal is to help every child achieve the best possible quality of life.
When to Seek Medical Advice
If your child shows signs of unusual muscle weakness, delayed motor development, or if there is a family history of SMA, early consultation is essential.
Schedule a screening and consultation with a pediatric neurologist at Phyathai 2 Hospital. Early detection and treatment can make a life-changing difference.
