Spinal muscular atrophy (SMA)
Out of every 10,000 births, one baby is born with spinal muscular atrophy (SMA). SMA is a genetic disease that affects the part of the nervous system that controls voluntary muscle movement. It is cause by malfunctioning genes that affect how nerve cells and muscle cells communicate across the neuromuscular junction-the place where nerve cells meet muscle cells. Patients with SMA can have severe muscle weakness in the upper arms, legs, and shoulders and in some instances SMA may lead to paralysis or death. SMA has also been linked to the development of spinal disorders similar to scoliosis, read below to learn more. 1
SMA is broken into 4 groups, based on the patient’s age and disease severity1:
- SMA type 1
- SMA type 2
- SMA type 3
- SMA type 4
SMA type 1 (Werdnig-Hoffmann disease)
SMA type 2
SMA type 3 (Kugelberg-Welander disease)
SMA type 4
Since SMA is rare, it is important to rule out other diseases that it may be mistaken for, such as Prader-Willi syndrome, acute hypoxic ischemic encephalopathy, neonatal sepsis, and dyskinetic or metabolic conditions. To confirm SMA, often a family history is needed, a physical examination is done, and other tests may be performed, including:
- Testing of reflexes
- Brain MRI
- Muscle biopsy
- Metabolic testing
- Electromyography (EMG), to test the electrical activity of skeletal muscles
- Genetic testing to identify the affected genes and SMA type
Currently, nusinersen is the only FDA-approved treatment for SMA in children and adults. Before initiating any therapy, patients or parents of children with SMA should consult with a board-certified neurologist who specializes in neuromuscular diseases.
Catalyst Pharmaceuticals is conducting clinical trials into amifampridine phosphate for the treatment of SMA.
It’s important that note that parents who have a child affected by SMA have a 1 in 4 chance that their next child will inherit the disease. It is recommended that those parents undergo prenatal screening for SMA.
- D’Amico A, Mercuri E, Tiziano FD, Bertini E. Spinal muscular atrophy. Orphanet J Rare Dis. 201;6:71.
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