What are the other Names for this Condition? (Also known as/Synonyms)

• Glycogen Storage Disease Type VI
• GSD6
• Hepatic Glycogen Phosphorylase Deficiency

What is Hers Disease? (Definition/Background Information)

• Hers Disease is very infrequent congenital disorder that is characterized by the inability of the liver to breakdown glycogen (a derivative of glucose)
• Due to this inability, the normal functioning of the liver is affected, which results in the buildup of large quantities of glycogen. This leads to swollen liver, low blood sugar, and other signs and symptoms
• Often the symptoms may be mild, making it very difficult to diagnose Hers Disease. A liver biopsy may be required to assess liver damage and the extent of the disorder
• Hers Disease is treated by ensuring proper dietary control, which is essential to maintain blood sugar to normal levels. This has to be practiced lifelong
• However, as the child grows into an adult, the symptoms may become mild, and generally, severe complications are not observed

Who gets Hers Disease? (Age and Sex Distribution)

• Hers Disease is an extremely rare genetic condition that affects children at birth
• Both male and female genders are at risk for Hers Disease
• All racial and ethnic groups may be affected; however, it is seen with a higher incidence in Old Order Mennonite group (of European origin, with a prevalence rate of 1 in 1000)

What are the Risk Factors for Hers Disease? (Predisposing Factors)

• Hers Disease is transmitted genetically from the parents to their offspring; hence those with a family history of the condition are at a high risk

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Hers Disease? (Etiology)

Hers Disease is a genetic disorder that is inherited in an autosomal recessive pattern.

• In this disorder, there are genetic mutations in the PYGL gene, which is responsible for the production of a certain type of enzyme (protein) in the liver
• Anomalies in the production of this enzyme mean that the liver cells are unable to function properly and there is accumulation of glycogen within them
• This results in the characteristic signs and symptoms of Hers Disease (also known as Glycogen Storage Disease Type VI)

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children, born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Hers Disease?

Hers Disease is a congenital condition that is manifested at birth. The signs and symptoms of this disorder are observed during the infancy stage itself. It may be mild or severe and may include the following:

• Enlarged liver
• Low levels of blood sugar with accompanying signs and symptoms
• High levels of lactic acid in the body leading to a condition called lactic acidosis, especially observed with poor dietary intake

How is Hers Disease Diagnosed?

The diagnosis of Hers Disease may involve the following tests and exams:

• Complete physical examination with evaluation of medical history
• Urine and blood analysis
• Radiographic studies (for skeletal survey) that may include CT or MRI scan of the affected region
• Imaging studies to diagnose liver enlargement
• Ischemic forearm test
• Liver biopsy: A biopsy is performed and sent to a laboratory for a pathological examination, who examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis
• Genetic tests and analysis to detect mutations

Note: Hers Disease is difficult to diagnose, especially if the symptoms are very mild.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Hers Disease?

The complications due to Hers Disease may include: 

• Severe case of swollen liver that can result in death (hepatic failure)
• Abnormally low blood sugar levels

How is Hers Disease Treated?

Currently, Hers Disease has no known cures, and hence, an individualized treatment is planned and provided (a case-by-case approach) to improve the quality of life, based on the specific conditions/complications that develop.

• Diet therapy: High protein diet with cornstarch is recommended to achieve normal blood sugar level, improve growth (including bone density), and normalize blood ketone levels
• Need-based supportive treatment

How can Hers Disease be Prevented?

• Currently, there are no specific methods or guidelines to prevent Hers Disease, since it is a genetic condition
• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders such as Hers Disease
• Regular medical screening at periodic intervals with tests, scans, and physical examinations are advised

What is the Prognosis of Hers Disease? (Outcomes/Resolutions)

• Hers Disease is an enzyme-related defect that is inherited; a lifelong treatment (particularly with respect to strict diet control) is necessary
• Severe cases where the liver is damaged, could lead to life-threatening situations
• However, as the individual moves from childhood to adulthood, the signs and symptoms of Hers Disease generally improve and health-related complications are rare (in most cases)

Additional and Relevant Useful Information for Hers Disease:

There are 8 types of glycogen storage diseases, all of which are related to enzyme deficiencies or defects; Hers Disease is Glycogen Storage Disease Type VI.