Glycogen storage syndrome type 0 caused by GYS2 gene variation and phenotypic differences between two siblings

OBJECTIVE To provide a basis for genetic counseling and clinical precision therapy by exploring the genetic etiology of a child with recurrent hypoglycemia convulsion accompanied by language retardation. METHODS Peripheral blood samples were obtained from the proband, his sister and his parents. Whole genomic DNA was extracted and analyzed by the whole exon gene sequencing and confirmed by Sanger sequencing. RESULTS The proband and his sister were found to carry compound heterozygous variants c.731T>A (p.M244L) and c.928G>A (p.G244S) of the GYS2 gene, which had not been reported in the past, the c.731T>A (p.M244L) site was derived from the maternal heterozygous mutation, while c.928G>A (p.G244S) site from the father heterozygous mutation. CONCLUSION The compound heterozygous variants c.731T>A (p.M244L) and c.928G>A (p.G244S) of the GYS2 gene were the genetic cause of glycogen storage syndrome type 0 in children, providing basis for family genetic counseling. When the patient had Hypoglycemia often accompanied with convulsions, which was easy to be misdiagnosed as seizures, and the antiepileptic treatment was ineffective. After genetic diagnosis, the seizure can be controlled by improving diet to maintain blood glucose stability.