RESEARCH ARTICLE Creatine Transporter Defect Diagnosed by Proton NMR Spectroscopy in Males With Intellectual Disability Maria Antonietta Mencarelli,1,2 Maria Tassini,3 Marzia Pollazzon,1 Antonio Vivi,3 Marco Calderisi,3 Michele Falco,4 Marco Fichera,4 Lucia Monti,5 Sabrina Buoni,6 Francesca Mari,1,2 Udo Engelke,7 Ron A. Wevers,7 Joussef Hayek,6** and Alessandra Renieri1,2* 1Medical Genetics, Department of Biotechnology, University of Siena, Siena, Italy 2Medical Genetics, Azienda Ospedaliera Universitaria Senese, Siena, Italy 3The NMR Center University of Siena, Siena, Italy 4Laboratory of Genetic Diagnosis, IRCCS Associazione Oasi Maria Santissima, Troina, Italy 5Unit of Diagnostic and Therapeutic Neuroradiology and Inter Departmental Center of Nuclear Magnetic Resonance, Azienda Ospedaliera Senese, Siena, Italy 6Child Neuropsychiatry, Azienda Ospedaliera Senese, Siena, Italy 7Laboratory of Genetic Endocrine and Metabolic Diseases, Department of Laboratory Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands Received 7 January 2011; Accepted 23 June 2011 Creatine deﬁciency syndrome due to mutations in X-linked SLC6A8 gene results in nonspeciﬁc intellectual disability (ID). Diagnosis cannot be established on clinical grounds and is often based on the assessment of brain creatine levels by magnetic resonance spectroscopy (MRS). Considering high costs of MRS and necessity of sedation, this technique cannot be used as a ﬁrst level-screening test. Likewise, gene test analysis is time consuming and not easily accessible to all laboratories. In this article feasibility of urine analysis (creatine/creatinine (Cr/Crn) ratio) performed by nuclear magnetic resonance (NMR) as a ﬁrst level-screening test is explored. Before running a systematic selection of cases a preliminary study for further molecular analysis is shown. NMR urine spectra (n ¼ 1,347) of male patients with an ID without a clinically recognizable syndrome were measured. On the basis of abnormal Cr/Crn ratio, three patients with the highest values were selected for molecular analysis. A conﬁrmatory second urine test was positive in two patients and diagnosis was further conﬁrmed by a decreased brain creatine level and by SLC6A8 gene analysis. A de novo muta- tion was identiﬁed in one. Another patient inherited a novel mutation from the mother who also has a mild ID. A repeat urine test was negative in the third patient and accordingly creatine level in the brain and SLC6A8 gene analysis both gave a normal result. We conclude that Cr/Crn ratio measured by NMR for male patients represents a rapid and useful ﬁrst level screening test preceding molecular analysis. 2011 Wiley-Liss, Inc. Key words: creatine deﬁciency syndrome; SLC6A8; magnetic resonance spectroscopy; NMR urine 2011 Wiley-Liss, Inc. How to Cite this Article: Mencarelli MA, Tassini M, Pollazzon M, Vivi A, Calderisi M, Falco M, Fichera M, Monti L, Buoni S, Mari F, Engelke U, Wevers RA, Hayek J, Renieri A. 2011. Creatine transporter defect diagnosed by proton NMR spectroscopy in males with intellectual disability. Am J Med Genet Part A 155:2446–2452. INTRODUCTION Creatine deﬁciency syndrome caused by SLC6A8 gene mutations was ﬁrst described in 2001 by Salomons et al. [2001]. These authors characterized the presence of a mutation in the X-linked SLC6A8 gene in one patient with intellectual disability (ID) with absence of creatine in brain MRS and increased creatine in urine and plasma. Grant sponsor: Telethon; Grant numbers: GTB07001, GP06170. Maria Antonietta Mencarelli and Maria Tassini contributed equally to this work. *Correspondence to: Alessandra Renieri, Medical Genetics, Department of Biotechnology, University of Siena, Siena, Italy. E-mail: renieri@unisi.it **Correspondence to: Joussef Hayek, Child Neuropsychiatry, Azienda Ospedaliera Senese, Siena, Italy. E-mail: j.hayek@ao-siena.toscana.it Published online 9 September 2011 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ajmg.a.34208 2446