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Open AccessCase Report

A Case of Suspected Hyperphenylalaninemia at Newborn Screening by Tandem Mass Spectrometry during Total Parenteral Nutrition

1
Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy
2
Department of Medical, Oral and Biotechnological Sciences, University ‘‘G. d’Annunzio’’ of Chieti-Pescara, 66100 Chieti, Italy
3
Department of Medicine and Aging Science, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy
4
Department of Pediatrics, “Spirito Santo” Hospital, 65100 Pescara, Italy
5
Department of Maternal and Child Health, Neonatal Intensive Care Unit NICU, “Spirito Santo” Hospital, 65100 Pescara, Italy
6
Metabolic Diseases Unit, Bambino Gesù Children Hospital and Research Institute, 00165 Rome, Italy
7
Department of Psychological, Health and Territory Sciences, School of Medicine and Health Sciences, “G. d’Annunzio” University, 66100 Chieti, Italy
*
Author to whom correspondence should be addressed.
Metabolites 2020, 10(2), 44; https://doi.org/10.3390/metabo10020044
Received: 19 December 2019 / Revised: 17 January 2020 / Accepted: 21 January 2020 / Published: 24 January 2020
(This article belongs to the Special Issue Applications of Metabolomics in Maternal and Child Health)
Phenylketonuria (PKU) is a rare autosomal recessive condition affecting about 1 in 10,000 people in the Europe, with a higher rate in some countries, like Ireland and Italy. In Italy, newborn screening (NBS) by MS/MS allows the diagnostic suspicion of PKU and its variants (Hyperphenylalaninemia (HPA), Tetrahydrobiopterin (BH4) synthesis deficiency, and Tetrahydrobiopterin (BH4) recycling deficiency) through the quantification of Phenylalanine (Phe) and the Phenylalanine/Tyrosine (Phe/Tyr) ratio in dried blood Spot (DBS) samples. Here, we report a case of an HPA whose suspicion was possible with expanded NBS, even if the normal-weight newborn was in total parenteral nutrition (TPN). It is known that TPN may present metabolic alterations, mainly for amino acids at NBS in MS/MS, frequently causing false positives. Actually, TPN is considered a special protocol in NBS, requiring several sample collections. In particular, a DBS sample is required before TPN, at basal time point (48 h after birth) and 72 h after the end of the procedure. In the case we report, even if the first DBS sample (before TPN) resulted negative, the repeated NBS tests revealed increased levels of Phe and dramatically high Phe/Tyr ratio. Thus, the newborn was recalled, and the NBS test was repeated several times before that HPA suspicion was confirmed by other specific biochemical tests. This case highlights the importance of Phe/Tyr ratio, only detectable by MS/MS analysis, in supporting the diagnostic suspicion during amino acids administration in the neonatal period.
Keywords: phenylketonuria; hyperphenylalaninemia; inborn error of metabolism; mass spectrometry; metabolomics; LC–MS/MS phenylketonuria; hyperphenylalaninemia; inborn error of metabolism; mass spectrometry; metabolomics; LC–MS/MS
MDPI and ACS Style

Pieragostino, D.; Cicalini, I.; Di Michele, S.; Fusilli, P.; Cotugno, G.; Ferrante, R.; Bucci, I.; Dionisi-Vici, C.; Stuppia, L.; De Laurenzi, V.; Rossi, C. A Case of Suspected Hyperphenylalaninemia at Newborn Screening by Tandem Mass Spectrometry during Total Parenteral Nutrition. Metabolites 2020, 10, 44.

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