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 (
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]