Several genetic markers have been identified as predisposing factors in the aetiology of motor neuron disease, MND /ALS. Chief among these are mutations in the SOD1 gene but many other aberration of the genome have been implicated mainly in the form of structural variants (SVs). Comparison is made between sporadic MND/ALS and a similar degenerative disorder endemic on the island of Guam known to be caused by Cycad toxicity. The long incubation period of both conditions points to a complex time-dependent pathogenesis.