| Spinal muscular atrophy | |
|---|---|
| Other names | Autosomal recessive proximal spinal muscular atrophy, 5q spinal muscular atrophy |
 | |
| Location of neurons affected by spinal muscular atrophy in the spinal cord | |
| Specialty | Neurology |
| Symptoms | Progressive muscle weakness[1] |
| Complications | Scoliosis, joint contractures, pneumonia[2] |
| Types | Type 0 to type 4[2] |
| Causes | Mutation in SMN1[2] |
| Diagnostic method | Genetic testing[1] |
| Differential diagnosis | Congenital muscular dystrophy, Duchenne muscular dystrophy, Prader-Willi syndrome[2] |
| Treatment | Supportive care, medications[1] |
| Medication | Nusinersen, onasemnogene abeparvovec[3][4] |
| Prognosis | Varies by type[2] |
| Frequency | 1 in 10,000 people[2] |
Spinal muscular atrophy (SMA) is a group of neuromuscular disorders that result in the loss of motor neurons and progressive muscle wasting.[1] The severity of symptoms and age of onset varies by the type.[1] Some types are apparent at or before birth while others are not apparent until adulthood.[1] All generally result in worsening muscle weakness associated with muscle twitching.[1][3] Arm, leg and respiratory muscles are generally affected first.[3][5] Associated problems may include problems with swallowing, scoliosis, and joint contractures.[2][5] SMA is a leading genetic cause of death in infants.[4]
Spinal muscular atrophy is due to a genetic defect in the SMN1 gene.[1][2] They are generally inherited from a person's parents in an autosomal recessive manner.[1] In 2% of cases, one of the mutations occurs during early development and one is inherited from a parent.[6] The SMN1 gene encodes SMN, a protein necessary for survival of motor neurons.[5] Loss of these neurons prevents the sending of signals between the brain and skeletal muscles.[5] Diagnosis is suspected based on symptoms and confirmed by genetic testing.[1]
Treatments include supportive care such as physical therapy, nutrition support, and mechanical ventilation.[1] The medication nusinersen, which is injected around the spinal cord, slows the progression of the disease and improves muscle function.[1][3] In 2019, the gene therapy onasemnogene abeparvovec was approved in the US as a treatment for children under 24 months.[4] Outcomes vary by type from a life expectancy of a few months to mild muscle weakness with a normal life expectancy.[5] The condition affects about 1 in 10,000 people at birth.[2]
References edit
- ^ a b c d e f g h i j k l "Spinal muscular atrophy". Genetic and Rare Diseases Information Center (GARD) – an NCATS Program. Archived from the original on 23 January 2017. Retrieved 27 May 2019.
- ^ a b c d e f g h i "Spinal Muscular Atrophy". NORD (National Organization for Rare Disorders). Archived from the original on 7 March 2016. Retrieved 27 May 2019.
- ^ a b c d "Spinal Muscular Atrophy Fact Sheet | National Institute of Neurological Disorders and Stroke". NINDS. Archived from the original on 27 May 2019. Retrieved 27 May 2019.
- ^ a b c "FDA approves innovative gene therapy to treat pediatric patients with spinal muscular atrophy, a rare disease and leading genetic cause of infant mortality". FDA. 24 May 2019. Archived from the original on 1 September 2019. Retrieved 27 May 2019.
- ^ a b c d e "Spinal muscular atrophy". Genetics Home Reference. Archived from the original on 30 May 2019. Retrieved 27 May 2019.
- ^ Prior, Thomas W.; Leach, Meganne E.; Finanger, Erika (1993). "Spinal Muscular Atrophy". GeneReviews®. University of Washington, Seattle. Archived from the original on 27 November 2020. Retrieved 6 October 2020.