Please cite this article in press as: C. Cavicchi, et al., J. Pharm. Biomed. Anal. (2009), doi:10.1016/j.jpba.2009.03.001 ARTICLE IN PRESS G Model PBA-7170; No. of Pages 4 Journal of Pharmaceutical and Biomedical Analysis xxx (2009) xxx–xxx Contents lists available at ScienceDirect Journal of Pharmaceutical and Biomedical Analysis journal homepage: www.elsevier.com/locate/jpba Short communication Hypocitrullinemia in expanded newborn screening by LC–MS/MS is not a reliable marker for ornithine transcarbamylase deficiency C. Cavicchi a , S. Malvagia a , G. la Marca a,c , S. Gasperini a , M.A. Donati a , E. Zammarchi b,* , R. Guerrini a , A. Morrone a , E. Pasquini a a Metabolic and Muscular Unit, Clinic of Pediatric Neurology, A.O.U. Meyer, Florence, Italy b Department of Pediatrics, University of Florence, Meyer Children’s Hospital, Viale Pieraccini 24, 50139 Florence, Italy c Department of Pharmacology, Metabolic and Muscular Unit, Clinic of Pediatric Neurology, A.O.U. Meyer, Florence, Italy article info Article history: Received 26 January 2009 Received in revised form 2 March 2009 Accepted 3 March 2009 Available online xxx Keywords: Hypocitrullinemia Expanded newborn screening Ornithine transcarbamylase deficiency (OTCD) OTC gene Molecular analysis abstract In an expanded newborn screening program for inborn errors of metabolism by LC–MS/MS in Tuscany, six newborns out of 169,000 showed decreased blood citrulline levels. In one of them, molecular anal- ysis of the OTC gene identified the known p.Trp265Leu mutation, which is correlated with late-onset ornithine transcarbamylase deficiency (OTCD). Hypocitrullinemia is not a reliable marker for OTCD new- born screening, especially for late-onset forms that may exhibit normal citrulline levels. However, when hypocitrullinemia is detected in a newborn in whom intestinal dysfunction and prematurity have been excluded, OTCD should be investigated first because of the OTCD incidence (1:14,000) and the small size of the OTC gene coding sequence. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Screening programs exploring acylcarnitine and amino acid pro- files through tandem mass spectrometry (LC–MS/MS) in newborns can detect more than 30 inborn errors of metabolism. Citrulline, one of the amino acids checked in LC–MS/MS new- born screening, is synthesized mainly in the mitochondrial matrix of hepatocytes and to a lesser extent in the small intestine and kid- ney as an intermediate in the conversion of ammonia in the urea cycle and during nitric oxide production [1]. High blood citrulline levels may be suggestive of citrulline- mia type I (MIM 215700), citrullinemia type II (MIM 603471) or argininosuccinic aciduria (MIM 207900). On the other hand, low blood citrulline levels can be detected in defects in the first two steps of the urea cycle, such as ornithine transcarbamylase (OTC; MIM 311250) and carbamoyl phosphate synthetase I (CPSI; MIM 237300) deficiencies [1] and in N-acetylglutamate synthetase defi- ciency (NAGS; MIM 237310) [2,3], in some mitochondrial disorders, such as NARP (MIM 551500) [4] and MELAS (MIM 540000) [5] or in delta-1-pyrroline-5-carboxylate synthetase deficiency (P5CS; MIM 138250) [6]. These inborn errors are not currently included in con- * Corresponding author. Tel.: +39 055 5662543; fax: +39 055 5662849. E-mail address: enrico.zammarchi@unifi.it (E. Zammarchi). ventional newborn screening programs. However, the commonest causes of low citrulline are detected in premature infants or in sick babies such as those with pathological conditions involving the small intestine, i.e. short-bowel syndrome [7,8]. Ornithine transcarbamylase deficiency (OTCD) is the most com- mon urea cycle disorder with an X-linked inheritance (locus Xp21.1) and variable severity affecting both males and females [1]. The OTC gene, containing 10 exons, codes a 1062nt mRNA expressed only in the liver and intestine. So far, about 370 mutations, leading to neonatal or late-onset forms, have been identified in the OTC gene. Early diagnosis and treatment can improve prognosis by preventing possible acute metabolic decompensation and irreversible damage induced by hyperammonemia. Some reports have described OTCD patients identified through a selective screening program for inborn errors of metabolism [9,10] or born to a mother with known risk [11] or infants in whom results of newborn screening became available after clinical presentation [12,13]. Mass spectrometry is one the most effective method in newborn screening for inborn errors of metabolism. Herein, we report our experience in the monitoring of low citrulline levels in expanded newborn screening. During the last 6 years, 169,000 newborns were screened by LC–MS/MS in Tuscany and six babies were recalled for low blood citrulline levels. In one of them, OCTD was confirmed by molecular analysis. To our knowledge, this is the first case of 0731-7085/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jpba.2009.03.001