Report of a Novel Mutation of HPD Gene Related to Tyrosinemia type III Phenotype

Hereditary tyrosinemia type III is an uncommon inherited disorder of tyrosine metabolism caused by a deficiency of 4-hydroxyphenylpyruvate dioxygenase (HPD). This metabolic condition is passed down in an autosomal recessive pattern. Due to the rarity of the disease, the clinical presentation can be quite varied and unclear, but the primary symptoms are usually associated with elevated levels of tyrosine and phenolic metabolites, such as seizures, ataxia, and mental retardation. We presented the clinical, biochemical, and molecular features of a patient with tyrosinemia type III and his subsequent progress. Whole-exome sequencing revealed a novel HPD (276710) mutation (c.G1079C) in a homozygous pattern. Despite adhering to the prescribed diet, subsequent increased tyrosine level, the patient maintained normal neuropsychiatric development during the follow-up, raising questions about the effectiveness of a low-tyrosine diet. As a result, high tyrosine concentration may not act directly in neuronal damage of tyrosinemia type III patients.