Case report: adult-onset manifesting heterozygous glycogen storage disease type IV with dilated cardiomyopathy and absent late gadolinium enhancement on cardiac magnetic resonance imaging.

Background: Glycogen storage disease type IV (GSD IV; Andersen's disease) is a rare autosomal recessive disease caused by mutation in the GBE1 gene. Presentation of GSD IV varies on a continuum of severity and symptomatology ranging from neonatal death to mild adult-onset disease with variable involvement of hepatic, muscular, neurologic, dermatologic, and cardiac systems. Cardiomyopathy seen in GSD IV is also heterogeneous and its appearance on cardiac magnetic resonance imaging (CMR) is rarely described.

Case Summary: A 29-year-old man without previous medical history was admitted to our facility multiple times over 2 years for focal sensorimotor deficits, gout arthropathy, chronic hyperlactataemia and hyperuricaemia, and severe decompensated non-ischaemic cardiomyopathy complicated by episodes of thromboembolic organ infarction. Echocardiography and CMR showed severe biventricular failure with the presence of intraventricular thrombi with increased right ventricular trabeculation and absent late gadolinium enhancement. He underwent muscle biopsy which showed prominent glycogen in skeletal muscle followed by genetic testing showing a single heterozygous splicing mutation c.993-1G>T found at the junction of intron 7 and exon 8 of the GBE1 gene which had not previously been reported and was predicted to be pathologic. He was referred to a tertiary care centre with glycogen storage disease specialists but expired prior to establishing care at that facility.

Discussion: Discovery of GSD IV in our patient was unexpected due to a highly variant clinical presentation. Our case stresses the clinical heterogeneity of GSD IV and the importance of genetic sequencing studies in the evaluation of potential glycogen storage disease.