HPDL and neurodevelopmental disorder: One of the most recently identified genes is 4-HydroxyPhenylpyruvate Dioxygenase-Like (HPDL), a single-exon gene encoding a protein that has been associated with rare, progressive childhood-onset movement disorders, with a broad clinical spectrum ranging from severe neurodevelopmental disorder with progressive spasticity and brain white matter abnormalities (NEDSWA phenotype MIM #619026) to juvenile-onset HSP (SPG83, MIM #619027) [5,6,7,8,9,10,11].