Multiple voxel 1 H MR spectroscopy of phosphorylase-b kinase deficient patients (GSD IXa) showing an accumulation of fat in the liver that resolves with aging Paul E. Sijens 1, * , G. Peter Smit 2 , Marinus A.J. Borgdorff 2 , Peter Kappert 1 , Matthijs Oudkerk 1 1 Radiology, University Medical Center Groningen and University of Groningen, Hanzeplein 1, 9713 GZ, The Netherlands 2 Pediatrics, University Medical Center Groningen and University of Groningen, Hanzeplein 1, 9713 GZ, The Netherlands Background/ Aims: Phosphorylase-b deficient patients suffer from glycogen storage disease (GSD IXa) leading to liver enlargement which usually resolves during puberty and adolescence. This pathology has not yet been documented by 1 H MR spectroscopy (MRS) investigation. Methods: MRS of eight GSD IXa patients was performed in this study to assess whether or not liver fat content is ele- vated in GSD IXa and decreases with aging. An improvement in our MRS method compared with previous liver fat MRS studies is that we measured a plane of liver voxels at once rather than a single MRS voxel, yielding a reliable determination of liver fat content. Results: Fat contents of 3.4–10% were observed in young GSD IXa patients, as compared with 0.5–0.9% in controls, these dropped to control levels in patients past age 40 (r = À0.82; P < 0.01). Conclusions: Liver fat content is increased in glycogen storage disease (GSD IXa) and normalizes with ageing. Assessing liver fat levels in this population is a novel and interesting concept. This could potentially enhance the understanding of liver function in that 20% of the population who has increased liver fat. Ó 2006 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. Keywords: Glycogen storage disease; Hepatomegaly; Lipid metabolism; Magnetic resonance spectroscopy 1. Introduction The glycogen storage diseases [GSDs] affecting the liver, while forming a broad spectrum of clinical phe- nomena and biochemical abnormalities, have in com- mon that because of an enzyme deficiency glycogen- breakdown is impaired and hence glycogen accumulates in hepatocytes [1,2]. Episodes of hypoglycemia and enlargement of the liver (hepatomegaly) are the main findings in all hepatic GSDs, but apart from this the het- erogeneity of their presentation is considerable [1,3]. Biochemically, disturbances are seen in glucose-, fat-, and aminoacid-metabolism [1,3,4]. Lipid deposition has been observed in some of the GSDs, among others in the main subtype of GSD IX, X-linked phosphory- lase-b kinase deficiency type I/2 (GSD IXa)]. GSD IXa probably is the most frequent and the mildest of all hepatic GSDs. GSD IXa accounts for a broad range of clinical symptoms [5], ranging from growth retardation to life- threatening episodes of hypoglycemia, especially at young age. However, the clinical picture caused by GSD IXa generally is milder than that in the other hepatic glycogen storage diseases, with the exception of phosphorylase deficiency (GSD VI) [6]. The clinical features of GSD IXa are hepatomegaly, growth retarda- tion, delay in motor development, hypotonia, elevated 0168-8278/$32.00 Ó 2006 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jhep.2006.06.021 Received 21 March 2006; received in revised form 6 June 2006; accepted 28 June 2006; available online 22 August 2006 * Corresponding author. Tel.: +31 503613534; fax +31 503611798. E-mail address: p.e.sijens@rad.umcg.nl (P.E. Sijens). www.elsevier.com/locate/jhep Journal of Hepatology 45 (2006) 851–855