Glycogen storage disease type VI with a novel PYGL mutation: Two case reports and literature review

Rationale: Glycogen storage disease (GSD) type VI is a rare disease caused by the inherited deficiency of liver phosphorylase.

Patient concerns: The proband, a 61-month-old Chinese boy, manifested intermittent hematochezia, growth retardation, hepatomegaly, damage of liver function, mild hypoglycemia, and hyperlactatemia. The other patient was a 107-month-old Chinese girl with growth retardation, hepatomegaly, mild hypoglycemia, and hyperlactatemia. In order to further confirm the diagnosis, we conducted a liver biopsy and detected blood samples for their gene using IDT exon chip capture and high-throughput sequencing.

Diagnoses: According to the clinical symptoms, physical examination, laboratory examinations, liver biopsy, and the genetic test finding, the 2 patients were diagnosed GSD VI.

Interventions: They were treated mainly with uncooked cornstarch.

Outcomes: There were 2 mutations of PYGL gene in this pedigree. c.2467C>T (p. Q823X) and c.2178-2A>C occurred both in the proband and his second sister.

Lessons: As a novel mutation, c.2178-2A>C enriches the mutation spectrum of PYGL gene. The different degrees of elevated lactate is an unusual phenotype in GSD VI patients. It is not clear if this is caused by the new mutation of c. 2178-2A > C. Long-term complications remains to be observed.