Spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME), sometimes called Jankovic–Rivera syndrome, is a very rare neurodegenerative disease whose symptoms include slowly progressive muscle loss (atrophy), predominantly affecting proximal muscles, combined with denervation and myoclonicseizures.[1] Only 12 known human families are described in scientific literature to have SMA-PME.[2]
The condition was first described in 1979 by American researchers Joseph Jankovic and Victor M. Rivera.[5]
ASAH1 gene
The ASAH1 gene codes for acid ceramidase, an enzyme found in lysosomes. The lysosome breaks down acid ceramidase; the fatty acid component [6] is then used to produce myelin. Myelin is an insulating coating around the neurons in the body which helps to contain bioelectrical signals along a nerve cell's axon 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]