Spinal muscular atrophy (SMA) is caused by a homozygous deletion of the survival motor neuron (SMN)1 gene. The nearly identical SMN2 gene plays a disease modifying role. SMA is classified into four different subtypes based on age of onset and clinical course (SMA types 1-4). The natural history of early onset SMA types 1-3a has been studied extensively. Late onset SMA is rare and disease course has not been studied in detail.
Dept. of Neurology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, HP G 02.320, 85500, 3508, GA Utrecht, The Netherlands. s.piepers-2@umcutrecht.nl
