Since loss of function variants in the liver enzyme PAH are themost common causes of phenylketonuria, attempts have been made todesign pharmacological chaperones that can correct misfolded proteinvariants of PAH.5 TH inhibitors decreasethe production of catecholamines and have been tested as antihypertensives6 and in neurological/neuropsychiatric disorders,including infantile spasms7 and autism.8 The gene discussed is TH; the disease is pulmonary arterial hypertension.