Phenylalanine Hydroxylase Deficiency and Citrin Deficiency in a Chinese Infant

To the Editor： Tandem mass spectrometry （MS/MS）-based expanded newborn screening was first introduced in Pediatric Endocrinology/ Genetics of Xin Hua Hospital in 2003. The screening is expected to detect genetic disorders leading to a secondary increase in blood phenylalanine （Phe） in newborns. We reported a rare case in a Chinese infant with hyperphenylalaninemia （HPA） caused by phenylalanine hydroxylase （PAH） deficiency and neonatal intrahepatic cholestasis caused by citrin deficiency （NICCD）. This constellation of two different metabolic pathway defects in one patient has not been reported previously.