The American College of Medical Genetics and Genomics (ACMG) recommends that because SMA is found in all populations, carrier screening should be offered to couples of all races and ethnicities.
The ACMG suggests that the testing be performed either before conception or early in pregnancy to allow carriers to make informed reproductive choices.5
SMA in a disease of two genes: the determinant gene, SMN1, and the modifier gene, SMN2.
Watch video nowvideoWrapper1
SMA results from homozygous deletions or mutations involving the SMN gene at locus 5q13 of chromosome 5. There are many rare neuromuscular disorders (e.g., Lambert-Eaton myasthenic syndrome, affecting 0.05-0.08/100,000 people a year).8 These disorders may involve mutations in a variety of different genes that are not associated with 5q13.
The differential diagnosis of 5q spinal muscular atrophy includes, but is not limited to:9
Spinal cord disorders
Other metabolic myopathies:
Neuromuscular junction disorders
Other motor neuron diseases
Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.4
The characters shown are real patients and the required consent to use their stories has been obtained from the patients and families. Photographs are for illustrative purposes only.
1. Lefebvre S, Bürglen L, Reboullet S, et al. Identification and characterization of a spinal muscular atrophy-determining gene. Cell 1995;80(1):155-165.
2. Kolb SJ, Kissel JT. Spinal muscular atrophy. Arch Neurol 2011;68(8):979-984.
3. Lunn MR, Wang CH. Spinal muscular atrophy. Lancet 2008;371(9630):2120-2133.
4. National Organization for Rare Diseases. Spinal muscular atrophy. [online] 2012 [cited 2016 Apr 17]. Available from: URL: http://rarediseases.org/rarediseases/spinal-muscular-atrophy/.
5. Prior TW; Professional Practice Guidelines Committee. Carrier screening for spinal muscular atrophy. Genet Med 2008;10(11):840-842.
6. D’Amico A, Mercuri E, Tiziano FD, Bertini E. Spinal muscular atrophy. Orphanet J Rare Dis 2011;6:71.
7. Mercuri E, et al. Diagnosis and management of spinal muscular atrophy: Part 1: Recommendations for diagnosis, rehabilitation, orthopedic and nutritional care. Neuromuscl Disord 2018;28(2):103-115.
8. Wirtz PW, Nijnuis MG, Sotodeh M, et al. The epidemiology of myasthenia gravis, Lambert–Eaton myasthenic syndrome and their associated tumours in the northern part of the province of South Holland. J Neurol. 2003;250(6):698–701. doi: 10.1007/ s00415-003-1063-7
9. Darras BT, Royden Jones H Jr, Ryan MM, De Vivo DC, eds. Neuromuscular Disorders of Infancy, Childhood, and Adolescence: A Clinician’s Approach. 2nd Ed. London, UK: Elsevier; 2015.