Glycogen Storage Disease with Massive Left Ventricular Hypertrophy and Increased Native T1: a Case Report.

Background Glycogen storage disease (GSD) type IIIa is a rare autosomal recessive disorder resulting in the accumulation of abnormally structured glycogen in the liver, skeletal muscle, and cardiac muscle. Cardiovascular magnetic resonance (CMR) tissue characteristics in GSD have rarely been reported.Case summary We report a 24-year-old male patient suffering from recurrent palpitation and atypical chest pain for 5 years with suspected hypertrophic cardiomyopathy. Laboratory tests revealed an elevated creatine kinase, and physical exam revealed hepatosplenomegaly. Cardiovascular magnetic resonance demonstrated asymmetrical massive left ventricular hypertrophy with a maximal thickness of 34.6 mm in the septum. In the regions with focal late gadolinium enhancement (LGE) in the anterior septum, both native T1 and extracellular volume (ECV) are elevated. However, in the LGE-negative regions of the myocardium, native T1 was elevated without elevation in ECV (septum, 22.7%; free wall, 20.9%). Whole exome sequencing revealed a novel pathogenic homozygous nonsense variant of the AGL gene (c.4284 T > G, p. Tyr1428*), confirming the diagnosis of the patients as GSD type IIIa.Discussion This case showed increased diffuse native T1 but not ECV on CMR in LGE-negative myocardium in GSD, which indicates that the T1 value is increased with an accumulation of glycogen in the myocardium, but the ECV space was not expanded in this process. Genetic testing should be obtained in severe LV hypertrophy when multi-organ involvement is present, and myocardial tissue characterization is discrepant between T1 elevation and normal ECV to consider glycogen storage disorder.