Genetic analyses have identified biallelic variants in the 4-hydroxyphenylpyruvate dioxygenase-like ( HPDL ) gene as the cause of a neurodegenerative disease that resembles the primary coenzyme Q10 (CoQ10) deficiency syndromes. HPDL is structurally similar to the well-studied 4-hydroxyphenyl pyruvate dioxygenase (HPPD), an iron(II)/α-ketoacid-dependent enzyme. HPPD is known to catalyze the second step in the tyrosine metabolis...