Novel variants in Turkish patients with glycogen storage disease

Three novel SLC37A4 variants in glycogen storage disease type 1b and a literature review

Glycogen storage disease type 1b (GSD1b) is a rare genetic disorder, resulting from mutations in the SLC37A4 gene located on chromosome 11q23.3. Although the SLC37A4 gene has been identified as the pathogenic gene for GSD1b, the complete variant spectrum of this gene remains to be fully elucidated. In this study, we present three patients diagnosed with GSD1b through genetic testing. We detected five variants of the SLC37A4 gene in these three patients, with three of these mutations (p. L382Pfs*15, p. G117fs*28, and p. T312Sfs*13) being novel variants not previously reported in the literature. We also present a literature review and general overview of the currently reported SLC37A4 gene variants. Our study expands the mutation spectrum of SLC37A4, which may help enable genetic testing to facilitate prompt diagnosis, appropriate intervention, and genetic counseling for affected families.

Genotypic and phenotypic characteristics of 12 chinese children with glycogen storage diseases

Background: Glycogen storage diseases (GSDs) are known as a group of disorders characterized by genetic errors leading to accumulation of glycogen in various tissues. Since different types of GSD can sometimes be clinically indistinguishable, next generation sequencing is becoming a powerful tool for clinical diagnosis.

Methods: 12 patients with suspected GSDs and their parents were enrolled in this study. The clinical and laboratory data of the patients were reviewed. Causative gene variants were identified in the patients using whole exome sequencing (WES) and verified by Sanger sequencing.

Results: Genetic testing and analysis showed that 7 patients were diagnosed with GSD II (Pompe disease), 2 patients with GSD III, 1 patient with GSD VI, and 2 patients with GSD IXα. A total number of 18 variants were identified in 12 patients including 11 variants in GAA gene, 3 variants in AGL gene, 2 variants in PYGL gene and 2 variants in PHKA2 gene, of which 9 variants were reported and 9 variants were novel. SIFT, Polyphen-2, Mutation Taster, and REVEL predicted the novel variants (except GAA c.1052_1075 + 47del) to be disease-causing. The 3D structures of wild/mutant type GAA protein were predicted indicating that variants p. Trp621Gly, p. Pro541Leu, p. Ser800Ile and p. Gly293Trp might affect the proteins function via destroying hydrogen bonds or conformational constraints. Neither liver size nor laboratory findings allow for a differentiation among GSD III, GSD VI and GSD IXα.

Conclusion: Our study expanded the variation spectrum of genes associated with GSDs. WES, in combination with clinical, biochemical, and pathological hallmarks, could provide accurate results for diagnosing and sub-typing GSD and related diseases in clinical setting.

The biallelic novel pathogenic variants in AGL gene in a chinese patient with glycogen storage disease type III

BACKGROUND

Glycogen storage disease type III (GSD III) is a rare autosomal recessive glycogenolysis disorder due to AGL gene variants, characterized by hepatomegaly, fasting hypoglycemia, hyperlipidemia, elevated hepatic transaminases, growth retardation, progressive myopathy, and cardiomyopathy. However, it is not easy to make a definite diagnosis in early stage of disease only based on the clinical phenotype and imageology due to its clinical heterogeneity.

CASE PRESENTATION

We report a two-year-old girl with GSD III from a nonconsanguineous Chinese family, who presented with hepatomegaly, fasting hypoglycemia, hyperlipidemia, elevated levels of transaminases. Accordingly, Sanger sequencing, whole‑exome sequencing of family trios, and qRT-PCR was performed, which revealed that the patient carried the compound heterogeneous variants, a novel frameshift mutation c.597delG (p. Q199Hfs*2) and a novel large gene fragment deletion of the entire exon 13 in AGL gene. The deletion of AGL was inherited from the proband's father and the c.597delG variant was from the mother.

CONCLUSIONS

In this study, we identified two novel variants c.597delG (p. Q199Hfs*2) and deletion of the entire exon 13 in AGL in a Chinese GSD III patient. We extend the mutation spectrum of AGL. We suggest that high-throughput sequencing technology can detect and screen pathogenic variant, which is a scientific basis about genetic counseling and clinical diagnosis.