ALS2 and hereditary spastic paraplegia: Mutations in the ALS2 gene have been associated with the development of juvenile onset ALS, as well as a range of other conditions such as primary lateral sclerosis and hereditary spastic paraplegia (HSP; Eymard-Pierre et al., 2002; Panzeri et al., 2006), with 12 different mutations identified to contribute to the development of such conditions (Chandran et al., 2007).