ATP13A2 and multiple system atrophy: However, the phenotypic spectrum associated with genetic variants in ATP13A2 now becomes more and more complex since the (partial) loss of function leads to a whole range of clinical phenotypes, including previously comprised of KRS, NCL, multiple system atrophy (MSA)6, hereditary spastic paraplegia (SPG78)7–10, and juvenile-onset amyotrophic lateral sclerosis (ALS)11, as supported by both genetic and functional data, which makes the ATP13A2 gene a puzzling gene12.