Molecular diagnosis of glycogen storage disease and disorders with overlapping clinical symptoms by massive parallel sequencing.

Abstract

Glycogen storage disease (GSD) is an umbrella term for a group of genetic disorders that involve the abnormal metabolism of glycogen; to date, 23 types of GSD have been identified. The nonspecific clinical presentation of GSD and the lack of specific biomarkers mean that Sanger sequencing is now widely relied on for making a diagnosis. However, this gene-by-gene sequencing technique is both laborious and costly, which is a consequence of the number of genes to be sequenced and the large size of some genes. This work reports the use of massive parallel sequencing to diagnose patients at our laboratory in Spain using either a customized gene panel (targeted exome sequencing) or the Illumina Clinical-Exome TruSight One Gene Panel (clinical exome sequencing (CES)). Sequence variants were matched against biochemical and clinical hallmarks. Pathogenic mutations were detected in 23 patients. Twenty-two mutations were recognized (mostly loss-of-function mutations), including 11 that were novel in GSD-associated genes. In addition, CES detected five patients with mutations in ALDOB, LIPA, NKX2-5, CPT2, or ANO5. Although these genes are not involved in GSD, they are associated with overlapping phenotypic characteristics such as hepatic, muscular, and cardiac dysfunction. These results show that next-generation sequencing, in combination with the detection of biochemical and clinical hallmarks, provides an accurate, high-throughput means of making genetic diagnoses of GSD and related diseases.Genet Med 18 10, 1037-1043.