IPP is increased when the genes for the enzymes that process it like isopentenyl diphosphate isomerase 1 and 2 (IDI1 and IDI2) are disrupted in a copy number variant in amyotrophic lateral sclerosis [110], or when the protein is aggregated in Lewy bodies in the brain [111]. Here, IDI1 is linked to amyotrophic lateral sclerosis.