Hepatic glycogen storage disorders: what have we learned in recent years?

PURPOSE OF REVIEW

Glycogen storage disorders (GSDs) are inborn errors of metabolism with abnormal storage or utilization of glycogen. The present review focuses on recent advances in hepatic GSD types I, III and VI/IX, with emphasis on clinical aspects and treatment.

RECENT FINDINGS

Evidence accumulates that poor metabolic control is a risk factor for the development of long-term complications, such as liver adenomas, low bone density/osteoporosis, and kidney disease in GSD I. However, mechanisms leading to these complications remain poorly understood and are being investigated. Molecular causes underlying neutropenia and neutrophil dysfunction in GSD I have been elucidated. Case series provide new insights into the natural course and outcome of GSD types VI and IX. For GSD III, a high protein/fat diet has been reported to improve (cardio)myopathy, but the beneficial effect of this dietary concept on muscle and liver disease manifestations needs to be further established in prospective studies.

SUMMARY

Although further knowledge has been gained regarding pathophysiology, disease course, treatment, and complications of hepatic GSDs, more controlled prospective studies are needed to assess effects of different dietary and medical treatment options on long-term outcome and quality of life.

The natural history of glycogen storage disease types VI and IX: Long-term outcome from the largest metabolic center in Canada

OBJECTIVES

Glycogen storage disease (GSD) types VI and IX are caused by phosphorylase system deficiencies. To evaluate the natural history and long-term treatment outcome of the patients with GSD-VI and -IX, we performed an observational retrospective case study of 21 patients with confirmed diagnosis of GSD-VI or -IX.

METHODS

All patients with GSD-VI or -IX, diagnosed at The Hospital for Sick Children, were included. Electronic and paper charts were reviewed for clinical features, biochemical investigations, molecular genetic testing, diagnostic imaging, long-term outcome and treatment by two independent research team members. All information was entered into an Excel database.

RESULTS

We report on the natural history and treatment outcomes of the 21 patients with GSD-VI and -IX and 16 novel pathogenic mutations in the PHKA2, PHKB, PHKG2 and PYGL genes. We report for the first time likely liver adenoma on liver ultrasound and liver fibrosis on liver biopsy specimens in patients with GSD-VI and mild cardiomyopathy on echocardiography in patients with GSD-VI and -IXb.

CONCLUSION

We recommend close monitoring in all patients with GSD-VI and -IX for the long-term liver and cardiac complications. There is a need for future studies if uncooked cornstarch and high protein diet would be able to prevent long-term complications of GSD-VI and -IX.

Effect of clonidine on the height of a child with glycogen storage disease type VI: a 13 year follow-up study

A 9-month-old male was found to have hepatomegaly when he was treated by his doctor for bronchitis. At the age of 2 years and 3 months, glycogen storage disease (GSD) of type VI (GSD VI) was diagnosed in this patient. Despite the recommended diet therapy, his growth was not good, changing under or along the line of -2.0 SD. At the age of 6 years, oral clonidine therapy (0.15 mg/day, 0.2 mg/m2 body surface per day) was started. Six to 10 months after the initiation of clonidine therapy, his height began to increase more than the values for -2.0 SD and once reached the value for -1.0 SD at the age of 10 years. His growth rate and bone age increased. Clonidine therapy was continued regularly for 7 years until the age of 13 years, 11 months. At that time his development was normal and his height reached 150.8 cm (-1.34 SD). However, cessation of the treatment at the patient's free will resulted in a reduction of the growth rate at age 15 years 6 months. These observations suggest the effect of clonidine therapy on height. Side effects were not noted during the clonidine therapy. Other clinical and laboratory findings of GSD VI also completely improved during treatment. In conclusion, administration of clonidine could be another treatment modality in children with GSD, not only of type VI but also I and III.