A genetic neuromuscular disorder that affects motor neurons, nerve cells responsible for voluntary muscle control, is called Spinal Muscular Atrophy (SMA). Muscle wasting, or atrophy, is caused by the loss of motor neurons, which results in weakness or complete inability to move the muscles involved in walking, sitting, arm movement, and head control (“Spinal muscular atrophy”). Some types of SMA affect the hands and feet movement; others might make it difficult to swallow and breathe in the later stages of the disease (“Spinal muscular atrophy”). SMA can affect individuals from before birth to early adulthood, depending on the type of disease.
SMA disorders can be inherited through either recessive genes or dominant. Types from I to IV are inherited in an autosomal recessive manner, caused by mutations in the SMN1 gene. These mutations result in the insufficient production of functional full-length MN protein needed for the proper functioning of motor neurons (“SMA”).In addition, the severity of the disease is smoothed by extra copies of the SMN2 (“SMA”). Forms with an autosomal dominant manner include distal MSA type V with changes in BSCL2 and GARS, SMA-LED with changes in DYNC1H1, and an adult version of SMA with changes in VAPB. Genetic testing allows for SMA diagnosis before the symptoms develop.
General treatment of SMA targets the progression of symptoms, avoiding complications, and increasing a person’s quality of life. Physical therapy and various assistive equipment, like walkers or wheelchairs, are being used to address movement issues. Back braces may be used in case of scoliosis and other complications affecting the backbone. Special breathing exercises, cough machines, and chest physiotherapy assist a person’s lung functions, and a nutrition diet might help when swallowing becomes an issue. For SMA types I to IV, Nusinersen injection is the only FDA-approved drug treatment (“Spinal muscular atrophy”). Despite showing positive results, its effect is rather individual and, in some cases, might either have no impact at all or cause complications.
The research in the last decade significantly brightened the overall picture for the SMA types from I to IV. They target raising SMN protein to the required level using different approaches (“SMA”). For example, the lack of protein could be addressed by transferring additional SMN1 genes to the body. Another research is focused on modifying the protein produced by SMN2, which usually tends to be short and not functional (“SMA”). Such is the case with the Nusinersen injections, which adjust the RNA build inside SMN2 and alter protein production. Regarding the other SMA types, the research field includes the development of drugs with muscle targeting, newborn screening, and broad neuroprotection.
References
Spinal muscular atrophy. (n.d.) Genetic and Rare Diseases Information Center (GARD).
Spinal muscular atrophy (SMA). (n.d.) Muscular Dystrophy Association (MDA).