Spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME), sometimes calledJankovic–Rivera syndrome, is a very rareneurodegenerative disease whose symptoms include slowly progressive muscle loss (atrophy), predominantly affectingproximal muscles, combined withdenervation andmyoclonicseizures.[1] Only 12 known human families are described in scientific literature to have SMA-PME.[2]
The ASAH1 gene codes foracid ceramidase, an enzyme found inlysosomes. The lysosome breaks down acid ceramidase; the fatty acid component[6] is then used to producemyelin. Myelin is an insulating coating around the neurons in the body which helps to contain bioelectrical signals along a nerve cell'saxon and increase transmission rate.[7] In patients with SMA-PME, the ceramidase function decreases to 33.33% effective.[2] The lack of myelin resulting from the lack of acid ceramidase breakdown leads to nerve cell dysfunction.[citation needed]
