HPDL and neurodegenerative disease: The 4-hydroxyphenylpyruvate dioxygenase-like protein (HPDL) is a mitochondria-localized protein involved in the biosynthesis of coenzyme Q10 in the electron transfer system, and its variants have been reported to cause progressive neurodegenerative diseases such as neonatal leukoencephalopathy and hereditary spastic paraplegia.