DDHD2 and hereditary spastic paraplegia: In humans, genetic errors in metabolism of phospholipids, sphingolipids, and other complex lipids such as triacylglycerols can result in a number of neurologic symptoms such as but not limited to spasticity and weakness of the lower extremities, dementia, loss of vision, ataxia, epilepsy, encephalopathy, and lipid accumulations in the brain tissue in disorders such as hereditary spastic paraplegia (HSP) (via loss of ECT, EPT1, or DDHD2) (15, 16, 17), Sjogren-Larsson syndrome (via loss of ALDH3A2) (18, 19), and Chanarin–Dorfman syndrome (via loss of ABHD5) (18, 20).