A rare coexistence: tyrosinemia type III and Wolff–Parkinson–White syndrome

Abstract Objectives Tyrosinemia type III is an extremely rare autosomal recessive disorder of tyrosine metabolism caused by mutations in the HPD gene, which encodes 4-hydroxyphenylpyruvate dioxygenase (HPPD). Wolff–Parkinson–White (WPW) syndrome is a congenital cardiac conduction disorder characterized by the presence of an accessory atrioventricular pathway. While each condition is rare in isolation, their coexistence has not been previously reported. Case presentation We present a unique case of a 6-year-old boy with known WPW syndrome who was admitted with ketotic hypoglycemia after prolonged fasting and omission of propranolol doses. Metabolic work-up revealed persistently elevated plasma tyrosine levels. Genetic testing confirmed tyrosinemia type III due to a novel homozygous HPD variant c.559A>G (p.Asn187Asp). The persistence of the WPW pattern despite decreased plasma tyrosine levels suggests that there is no direct causal relationship. He was also diagnosed with attention-deficit/hyperactivity disorder, specific learning disorder, and borderline intellectual functioning. Conclusions This case highlights the importance of metabolic evaluation in pediatric patients presenting with unexplained hypoglycemia, particularly in the presence of pre-existing cardiac disorders.