The metabolic landscape of tetrahydrobiopterin metabolism disorders in the Republic of Ireland.

We present a case series of seven patients (5 males, 2 females, aged 7-38 yrs.) in Ireland with biopterin metabolism disorder. Five individuals had been diagnosed with dihydropteridine reductase (DHPR) deficiency and two with pyruvoyl tetrahydropterin synthase (PTPS) deficiency. While clinical symptoms were mainly neuro-developmental in nature, one of our patients with DHPR deficiency also had a mild pulmonary valve stenosis and patent arterial duct in infancy which subsequently resolved as a hitherto undescribed finding in this condition. Clinical outcomes in our patient cohort were overall satisfactory with the best outcomes in patients/siblings diagnosed on high-risk screening. In conclusion, early diagnosis, pathophysiology-driven treatments and frequent patient-specific treatment adjustments are crucial to sustain the best possible long-term outcomes. Ireland's cohort of tetrahydropterin metabolism disorders highlights that improved outcomes are achieved with an early diagnosis which may not be attainable through newborn screening alone.