Rare Endocrinology News
Spotlight On
Spinal Muscular Atrophy (SMA)
Spinal muscular atrophy (SMA) is a rare neuromuscular disorder that results in the loss of motor neurons and progressive muscle wasting
Prevalence
10/100,000
Age of Onset
ICD-10
G12.9
Inheritance
Autosomal dominant
Autosomal recessive
Mitochondrial/Multigenic
X-linked dominant
X-linked recessive
5 Facts you should know
FACT
The term spinal muscular atrophy (SMA) refers to a group of genetic disorders all characterized by degeneration of anterior horn cells and resultant muscle atrophy and weakness
FACT
The severity of SMA is highly variable and the clinical features can be classified into 4 main phenotypes on the basis of age of onset and maximum motor function achieved
FACT
The clinical severity of SMA correlates inversely with SMN2 gene copy number and varies from extreme weakness and paraplegia of infancy to a mild proximal weakness of adulthood
FACT
The incidence of SMA in the United States is 1:10,000/11,000 live births
FACT
SMA affects individuals of all ethnic groups
Interest over time
Google searches
Common signs & symptoms
Muscle Weakness
Hypotonia (Low Muscle Tone)
Poor Motor Development
Difficulty Breathing and Swallowing
Muscle Atrophy
Joint Contractures
Current treatments
Treatment for SMA may vary depending on the subtype of SMA and severity of symptoms, but generally focuses on supportive care to increase the person's quality of life. In general, treatment may include physical therapy and assistive equipment to increase mobility, such as leg braces, walkers, and wheelchairs. Back braces may be used to assist sitting and prevent scoliosis and other complications affecting the backbone. Special breathing exercises, cough machines, and chest physiotherapy can help maintain the function of the lungs and keep the airways clear of mucous, especially in times of illness. A dietitian may help support nutrition if eating or swallowing becomes difficult.
For SMA types 1, 2, 3, and 4, nusinersen (Spinraza) is the first and only FDA approved treatment. Continued treatment with nusinersen has been found to increase motor function and slow the progression of symptoms. Many babies and young children with types 1 and 2 are able to reach developmental milestones and maintain those milestones over time. In general, breathing problems, nutrition problems, and hospital admissions also decrease. Older children with type 3 and adults with type 4 have also been shown to benefit from continuous treatment with nusinersen, including, for some, regaining the ability to walk longer distances, improving arm movement, and slowing or stopping the progression of the disorder. Ongoing, long term medical studies continue to report improvements. However, response to treatment does vary and some people with SMA types 1, 2, 3, or 4 may not respond to the drug at all or may have medical complications that prevent use of the treatment.