title: Novel PHKG2 mutation causing GSD IX with prominent liver disease: report of three cases and review of literature.
abstract: Glycogen storage disease type IX (GSD IX) is a common form of glycogenosis due to mutations in PHKA1, PHKA2, or PHKB and PHKG2 genes resulting in the deficiency of phosphorylase kinase. The first two genes are X-linked while the latter two follow an autosomal recessive inheritance. The majority of cases of GSD IX are attributed to defects in PHKA2 which usually cause a mild disease. We report three patients with PHKG2-related GSD IX presenting with significant hepatic involvement, fibrosis, and cirrhosis. Interestingly, the homozygosity mapping resolved a dilemma about an erroneously normal phosphorylase kinase activity in patient 1. The novel mutation found in all the three patients (p.G220E) affects the catalytic subunit of the phosphorylase kinase. Increasing evidence shows that patients with PHKG2 mutations have a severe hepatic phenotype within the heterogeneous GSD IX disorder. Therefore, defect in PHKG2 should be considered in patients with suspected glycogenosis associated with significant liver fibrosis and cirrhosis.
authors: Medical Genetics Centre, Kuwait City, Kuwait.
authors: Buthainah
authors: B
authors: Albash
authors: Faiqa
authors: F
authors: Imtiaz
authors: Hamad
authors: H
authors: Al-Zaidan
authors: Hadeel
authors: H
authors: Al-Manea
authors: Mohammed
authors: M
authors: Banemai
authors: R
authors: R
authors: Allam
authors: Ali
authors: A
authors: Al-Suheel
authors: Mohammed
authors: M
authors: Al-Owain
mesh_terms: D005260:Female; D005838:Genotype; D006008:Glycogen Storage Disease / Q000235:genetics*; D006801:Humans; D007223:Infant; D008107:Liver Diseases / Q000235:genetics; D008297:Male; D009154:Mutation; D010641:Phenotype; D010764:Phosphorylase Kinase / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012529:Saudi Arabia
chemical_list: D010764:Phosphorylase Kinase