Spinal Muscular Atrophy (SMA)

The spinal muscular atrophy (SMA) is a neuromuscular disease with an autosomal recessive inheritance pattern, characterized by the gradual degeneration of the motor neurons in the spinal cord. This disease causes varying degrees of muscle weakness and atrophy, significantly impacting the quality of life of patients. In Hungary, 10-15 new children with SMA are born each year, indicating the relatively rare occurrence of the disease, yet it can have severe effects on the lives of families.

The underlying cause of SMA is a defect in the SMN1 (Survival Motor Neuron 1) gene, which plays a key role in the survival of motor neurons. When this gene does not function properly, the cells located in the anterior horn of the spinal cord die, leading to the cessation of nerve impulses reaching the muscles. The progression and manifestation of the disease can be categorized into different types, which vary depending on the age of the affected individual and the severity of symptoms.

Thus, spinal muscular atrophy is not just a medical diagnosis, but a complex condition that touches on numerous aspects, including diagnostic methods, treatment options, and the quality of life of patients. Knowledge of appropriate information and treatment options is crucial for patients and their families to ensure the best possible quality of life while living with the disease.

Symptoms and Clinical Presentation

The symptoms of spinal muscular atrophy encompass a wide spectrum and can vary according to the type of the disease. Muscle weakness gradually worsens and typically affects the proximal muscle groups, while the muscles of the hands and feet are less affected. In most cases, reflexes are diminished or completely absent, and muscle twitches (fasciculations) may appear, most commonly in the tongue or hand area. Scoliosis and difficulties in breathing and swallowing are also more common in the more severe forms of the disease.

It is important to note that SMA types have the least impact on cognitive abilities in adulthood, and the facial muscles remain unaffected. The symptoms of different SMA types may vary in timing and severity. In SMA type I, the earliest symptoms may appear at birth, while symptoms in SMA types III and IV may develop later, even during adolescence or adulthood.

The progression of the disease and the severity of symptoms greatly influence treatment options and the quality of life of the patient, making early diagnosis crucial for those living with SMA.

The Types of SMA

There are four main types of spinal muscular atrophy, categorized based on the onset of the disease and the severity of symptoms.

SMA type I, also known as Werdnig-Hoffmann disease, is the most strictly defined infantile form, typically presenting before six months of age. The affected infants exhibit muscle weakness noticeable at birth, associated with poor motor skills, such as the inability to hold up their head. Without treatment, the prognosis is extremely poor, but modern therapies like Zolgensma and Spinraza can significantly improve survival.

SMA type II, or intermediate form, appears between six months and one and a half years, where children may be able to sit but cannot walk. SMA type III, also known as Kugelberg-Welander disease, manifests after the second year of life, and the disease progresses slowly, potentially leading to mobility restrictions. Finally, SMA type IV refers to the adult form, which typically begins after the age of 30 and has a milder course with minimal impact on life expectancy.

These types not only affect the timing of symptom onset but also influence treatment options, making it important to know the precise type of diagnosis.

Diagnosis and Screening

The process of diagnosing spinal muscular atrophy is primarily based on molecular genetic testing today. The absence or mutation of two copies of the SMN1 gene is the most common diagnostic criterion. Electromyography (EMG) can help detect nerve abnormalities, while muscle biopsy is rarely needed today.

Prenatal diagnostic options allow for early detection of the disease if the mutation is known in the family. Newborn screening is also available and increasingly provided free of charge in many countries, including Hungary, to improve life expectancy through early, pre-symptomatic intervention.

Early diagnosis is crucial in managing the course of the disease, as pre-symptomatic treatments, such as gene therapy, offer significant advantages in later stages of the disease. Screening and diagnosis thus not only aid in understanding the disease but also in selecting the most effective treatment methods.

Treatment Options and Support

Although spinal muscular atrophy is an incurable disease, advancements in modern medicine have enabled its treatment. The most important treatment options include gene therapy, the use of SMN2 gene-modifying agents, and symptomatic and supportive therapy.

Zolgensma is a one-time intravenous dose that delivers a functioning copy of the SMN1 gene into the body. This therapy is particularly effective in the early stages of the disease. Spinraza (nusinersen) administered into the spinal canal enhances SMN2 protein production, while Risdiplam (Evrysdi) allows for oral administration, enabling long-term treatment.

Symptomatic treatment includes respiratory support, feeding assistance, physical therapy, rehabilitation, and orthopedic care. Scoliosis can be treated with bracing or surgery, while multidisciplinary care ensures collaboration among physiotherapists, dietitians, and orthopedic specialists, which is essential for improving the patient’s development and quality of life.

The effectiveness of treatment largely depends on the type of disease and the timing of therapy initiation. Thanks to modern treatment options, many children with SMA are able to sit independently, move, and attend school, providing them with significant advantages in their daily lives.