A novel frameshift PHKA2 mutation in a family with glycogen storage disease type IXa: A first report in Vietnam and review of literature

A novel PHKA2 variant in a Chinese boy with glycogen storage diseases type IXa

Background

Glycogen storage diseases (GSDs) are a group of heterogeneous inherited metabolic disorders with an incidence of 4%-5%. There are 19 types of GSDs, making diagnosis one of the greatest challenges.

Methods

The proband and his parents were referred to our hospital for genetic diagnosis. Ultrasound screening suggested hepatomegaly. A novel insertion variant NM_000292 c.1155_1156insT (p. 386N>*) in PHKA2 gene was identified using trio whole exome sequencing (Trio-WES), which resulted in the codon of amino acid 386 from asparagine to termination (p. 386N>*). The 3D mutant protein structure was predicted using AlphaFold, and the results showed that the truncated PHKA2 protein contained 385 of the 1,235 amino acids of the mature protein.

Conclusion

We describe a previously unreported case of a GSDs IXa type Chinese boy caused by a novel PHKA2 variant. This clinical case contributes to the understanding of the characteristics of GSDs type IXa and expands the variants spectrum of genes related to GSDs type IXa. Our findings demonstrated the significance of genetic testing in the diagnosis of GSDs.

Identification of a novel mutation in the PHKA2 gene in a child with liver cirrhosis

OBJECTIVES

Glycogen storage diseases (GSDs) are heterogeneous disorders caused by various enzyme deficiencies. GSD type IX α2, the most common subtype of GSD IX, is due to a deficiency of hepatic phosphorylase kinase. Herein we will report a novel mutation in this disease with an unusual presentation.

CASE PRESENTATION

we describe a 3-year-old boy who suffered from hepatomegaly, fatty liver disease, and liver cirrhosis. The cause of cirrhosis at a young age was unknown based on the laboratory data and liver biopsy, so we performed a targeted-gene sequencing (TGS) covering 450 genes involved in inborn metabolic diseases consisting of glycogen storage disorders genes with hepatic involvement. He was found out to have a rare novel pathogenic variant in the PHKA2 gene.

CONCLUSIONS

This novel variant c.2226+2T > C expands the mutational spectrum of the PHKA2 gene. Also, severe liver damage (cirrhosis) in patients with GSD- IX α2 has rarely been reported, which needs further discussion. We hypothesize that unidentified PHKA2 variants may be a rare cause of childhood liver cirrhosis.

Effects of Silymarin and Baicalein on Glycogen Storage in the Hepatocytes of Rat Models of Hepatic Injury

Background: An association has been reported between hepatitis and glycogen storage problems. Glycogen storage disease (GSD) type I is induced by G6PD deficiency. Silymarin and baicalein, as herbal agents, have hepatoprotective and antioxidant potentials. Objectives: In this study, we assessed the effects of these herbs on liver glycogen storage problems and hepatitis. Methods: Twenty male rats kept under standard laboratory conditions were divided into four groups, including healthy (control) and hepatotoxicity treated with silymarin, baicalein, or none. The levels of ALT, AST, ALP, LDL, HDL, VLDL, TG, Cho, IL-1β, IL-6, and TNF-α were measured, and the expression levels of G6PD, CTGF, HMGB1, and P53 were determined. Also, liver histopathology was examined. Results: Treatment with silymarin and baicalein reduced the serum levels of ALT, AST, ALP, LDL, VLDL, TG, Cho, IL-1β, IL-6, and TNF-α. Silymarin increased G6PD gene expression, and both silymarin and baicalein reduced CTGF, P53, and HMGB1 gene expressions, but silymarin and baicalein had no effects on glycogen storage of hepatocytes. Conclusions: Baicalein and silymarin showed anti-inflammatory effects and could control inflammation and necrotic factors, but they did not affect hepatic glycogen storage.

Whole Exome Sequencing as a Diagnostic Tool for Unidentified Muscular Dystrophy in a Vietnamese Family

Muscular dystrophies are a group of heterogeneous clinical and genetic disorders. Two siblings presented with characteristics like muscular dystrophy, abnormal white matter, and elevated serum creatine kinase level. The high throughput of whole exome sequencing (WES) makes it an efficient tool for obtaining a precise diagnosis without the need for immunohistochemistry. WES was performed in the two siblings and their parents, followed by prioritization of variants and validation by Sanger sequencing. Very rare variants with moderate to high predicted impact in genes associated with neuromuscular disorders were selected. We identified two pathogenic missense variants, c.778C>T (p.H260Y) and c.2987G>A (p.C996Y), in the LAMA2 gene (NM_000426.3), in the homozygous state in two siblings, and in the heterozygous state in their unaffected parents, which were confirmed by Sanger sequencing. Variant c.2987G>A has not been reported previously. These variants may lead to a change in the structure and function of laminin-α2, a member of the family of laminin-211, which is an extracellular matrix protein that functions to stabilize the basement membrane of muscle fibers during contractions. Overall, WES enabled an accurate diagnosis of both patients with LAMA2-related muscular dystrophy and expanded the spectrum of missense variants in LAMA2.