Glycogen Storage Diseases
The Glycogen Storage Diseases (“GSD”) are rare genetic metabolic disorder that affects how a type of sugar in the body, called “glycogen,” is stored and broken down. What breaks down the glycogen are enzymes in the cells of the body. They control how glycogen is stored and metabolized. When those enzymes are absent or don't work properly, that results in an abnormal accumulation (“storage”) of glycogen in different organs and tissues in the body, especially the liver and muscles. That causes dysfunction in those organs and tissues. There are many different types of GSD, depending on what enzymes are abnormal or missing and what body organs are affected.
Types of GSD
There are at least 13 different types of glycogen storage disease. The Cleveland Clinic has compiled a list of some of the more common types and what organs are typically affected. [Ref: https://my.clevelandclinic.org/health/diseases/15553-glycogen-storage-disease-gsd]
- Type 0 (Lewis' disease) – Liver.
- Type I (von Gierke's disease) Type Ia – Liver, kidneys, intestines; Type Ib – Liver, kidneys, intestines, blood cells.
- Type II (Pompe's disease) – Muscles, heart, liver, nervous system, blood vessels.
- Type III (Forbes-Cori disease) – Liver, heart, skeletal muscles, blood cells.
- Type IV (Andersen's disease) – Liver, brain, heart, muscles, skin, nervous system.
- Type V (McArdle's disease) – Skeletal muscles.
- Type VI (Hers' disease) – Liver, blood cells.
- Type VII (Tarui's disease) – Skeletal muscles, blood cells.
- Type IX – Liver.
- Type XI (Fanconi-Bickel syndrome) – Liver, kidneys, intestines.
Type I (Von Gierke disease) is the most common type of glycogen storage disease, and accounts for 90% of all glycogen storage disease cases.
Symptoms of GSD
The symptoms of glycogen storage disease depend on the kind of enzymes that are abnormal or missing, which organ systems are involved, the age of onset and how rapidly or slowly the disease progresses. While there are no specific treatments for many of the different types of GSD (but see “Pompe's disease” below) and no cures, a dietary regimen may help many patients to control their symptoms.
In a rare type of GSD called Pompe's disease (type II), which is estimated to occur at 1 in every 40,000 births, inherited mutations in a gene that makes an enzyme called acid alpha-glucosidase (GAA).results in an often fatal disorder in infants and children that severely impairs the heart and skeletal muscles.
Adult onset Pompe's disease, which begins later in life, has a much better prognosis. In general, the later the age of onset of Pompe's, the slower the progression of the disease.
McCardle's disease (type V) affects muscles, where the accumulation of glycogen in muscles results in symptoms such as muscle weakness and cramps, especially with exercise. Hypoglycemia may cause symptoms such as lightheadedness, dizziness, fainting, sweating, tremor, drowsiness, and confusion.
Other symptoms that occur with GSD include tiredness, slow growth in children, abnormal bleeding, bruising, and blood clotting, heat intolerance, liver problems, kidney problems, hyperlipidemia, increased infections, shortness of breath and other lung problems, cardiac failure, gout (because of uric acid elevation), intestinal problems, and mouth sores. Id.
Glycogen Storage Disease causes enlargement of the liver (hepatomegaly), low blood glucose (hypoglycemia), muscle weakness, and/or growth retardation in infants and children.
The diagnosis of GSD is often made or confirmed by genetic testing and tissue biopsy (e.g., muscle, liver) with measurement of glycogen content and whether certain enzymes that break down glycogen are missing.
GSD is inherited when both parents have defective genes for a GSD.
In most types of GSD, there are no specific medications to treat the different types of GSD, and doctors have not found how to “fix” the abnormal genes or enzymes that cause the problem.
In such patients, dietary management can be helpful when GSD affects the liver. Treatment includes taking regular doses of uncooked cornstarch, nutritional supplements, and eating small, frequent meals that are low in sugar, which may help prevent hypoglycemia and excess glycogen storage in the liver.
Some patients with GSD develop progressive liver failure (e.g. type II and IV) from the storage of excessive amounts of glycogen in the liver and eventually may require liver transplant. Heart disease and pulmonary failure are other potentially fatal complications of GSD.
Research In Pompe's disease (type II) has led to the discovery of the GAA gene that is responsible for many of its clinical manifestations, and this has allowed the development of enzyme replacement therapy, including Myozyme (for infants) and Lumizyme (>8 years of age) that have been approved for treatment of Pompe's, with hopeful results in clinical trials. [Ref: Hahn, S. et al. “Efficacy, safety profile, and immunogenicity of alglucosidase alfa produced at the 4,000-liter scale in US children and adolescents with Pompe disease: ADVANCE, a phase IV, open-label, prospective study.” Genet Med 20, 1284–1294 (2018). https://doi.org/10.1038/gim.2018.2.]
Disability Benefits in GSD
If you are filing for Social Security disability benefits on behalf of an infant or child with a severe form of Pompe's disease (type II), you may be eligible for benefits (SSDI), including SSA's Compassionate Allowance program, which may entitle you to obtain benefits in a few weeks.
For adults with Pompe's disease (or other forms of GSD), in order to qualify for long-term disability (LTD) benefits under the Social Security Disability program or under an employer-sponsored group disability plan (ERISA), you must support your claim with credible medical records that document your diagnosis, symptoms, and how your symptoms affect your ability to perform your occupation or any other occupation. If you have symptoms such as chronic fatigue, weakness, lightheadedness, dizziness, drowsiness, or confusion, and if you are unable to perform even “sedentary work” (i.e., a desk job), you may qualify for LTD benefits under SSDI or ERISA.
Medical documentation is critically important in qualifying for disability benefits. That's the heart of any disability case, and it's important to work with your doctor to get the necessary clinical documentation into your medical records.
At Law Med, we understand the legal and medical aspects of Glycogen Storage Disease and other medical conditions and can work with your doctor to help you get your disability benefits.