SMA type 3
- juvenile spinal muscular atrophy is an uncommon autosomal recessive disorder of the lower motor neurones
- onset occurs between 2 and 17 years. It is characterised by wasting and weakness of proximal limb muscles. The deep tendon reflexes are decreased or absent. Fasciculations of the tongue may be occur
- children and adults with type 3 SMA, also referred to as Kugelberg-Welander disease, are able to walk unassisted at some point during their lifetime
- present with progressive proximal weakness of the legs more than the arms
- leg weakness may necessitate the need of a wheelchair at some point
- unlike, type 2, these individuals are mostly spared the comorbities of scoliosis and have little or no respiratory muscle weakness
- cognition and life expectancy are not altered in this group
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
- most common SMA, accounting for over 95% of cases, is an autosomal recessive disorder that results from a homozygous deletion or mutation in the 5q13 survival of motor neuron (SMN1) gene
- clinical severity of SMA correlates inversely with SMN2 gene copy number and varies from an extreme weakness and paraplegia of infancy to a mild proximal weakness of adulthood
- Sugarman EA, et al. Pan-ethnic carrier screening and prenatal diagnosis for spinal muscular atrophy: clinical laboratory analysis of >72,400 specimens. Eur J Hum Genet. 2012; 20(1):27–32.
- Kolb JS, Tissel SpinalJT. Muscular Atrophy. Neurol Clin. 2015 November ; 33(4): 831–846.
Last edited 03/2020 and last reviewed 03/2020