Metabolic Myopathies

Debrancher enzyme deficiency (Cori or Forbes disease)

What is debrancher enzyme deficiency (Cori or Forbes disease, glycogenosis type 3)?

This disease is a metabolic muscle disorder, a group of diseases that interferes with the processing of food (in this case, carbohydrates) for energy production.

What are the symptoms of debrancher enzyme deficiency?

This disease principally affects the liver. It causes swelling of the liver, slowing of growth, low blood sugar levels and, sometimes, seizures.

In children, these symptoms often improve around puberty. Muscle weakness may develop later in life, and is most pronounced in the muscles of the forearms, hands, lower legs and feet. Weakness often is accompanied by loss of muscle bulk and exercise intolerance. The heart can be affected as well.

What causes debrancher enzyme deficiency?

The disorder is caused by a defect in the debrancher enzyme gene, which interferes with the breakdown of glycogen (stored sugar) in the muscles and liver. For more, see Causes/Inheritance.

What is the progression of debrancher enzyme deficiency?

This disease can begin anywhere from infancy to the 50s and is slowly progressive. The infantile-onset form may be life-threatening in childhood.

What is the status of research on debrancher enzyme deficiency?

Researchers on metabolic diseases of muscle are making progress on a number of fronts, including:

• better diagnosis to allow for earlier identification of at-risk individuals and earlier treatment;
• continued examination of the role of exercise and diet in metabolic diseases;
• development of animal models of metabolic diseases, both to improve understanding of the diseases and to test possible treatments;
• development of enzyme replacement therapies; and
• development of gene therapies.