Impact of high-dose vitamins on a patient with hyperornithinemia-hyperammonemia-homocitrullinuria syndrome

Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a rare autosomal recessive metabolic disorder caused by a mutation of SLC25A15 encoding for the mitochondrial ornithine carrier. Recent study suggested that impaired mitochondrial function may play a major role in central nervous system impairment in HHH syndrome. We hypothesized that if the mitochondrial dysfunction was associated with neurological impairment in HHH syndrome, antioxidants might be effective to avoid aggravation of the brain injury. We presented the clinical outcome in a patient with HHH syndrome undergoing a high-dose vitamin treatment and discussed the effect of this treatment. The male patient was definitively diagnosed by compound heterogeneous pathogenic variants in the SLC25A15 gene. He was started vitamin B1, C and E therapy at age of 3 years. The blood lactate (Lac) levels gradually decreased and serum β-hydroxybutyrate/acetoacetate (β-OHB/AcAc) ratio also decreased at age of 7 years. A verbal development score in Kyoto Scale of Psychological Development was 65 at age of 3 years. However, quotient of Verbal Comprehension Index in Wechsler Intelligence Scale for Children - Fourth Edition increased to 109 at age of 7 years during this vitamin therapy. The outcome in our patient suggested that high-dose vitamin therapy might contribute to preventing cognitive disability. Moreover, the decreased blood Lac level and serum β-OHB/AcAc ratio also suggested that the effect of this therapy might be due to improving the mitochondrial function such as citric acid cycle . This case report suggest that the high-dose vitamin therapy may enhance mitochondrial function in HHH syndrome.