Metabolic Myopathies

Phosphofructokinase deficiency (Tarui disease)

What is phosphofructokinase deficiency (Tarui disease, glycogenosis type 7)?

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

What are the symptoms of phosphofructokinase deficiency?

The condition results in exercise intolerance, with pain, cramps and, occasionally, myoglobinuria (acute muscle breakdown leading to rust-colored urine). Symptoms are very similar to those of phosphorylase deficiency, but people with this disorder are less likely to experience the “second wind” phenomenon.

A carbohydrate meal typically worsens exercise capacity in this condition by lowering blood levels of fats, which are the major muscle energy fuels for those with the disorder.

A partial deficiency of phosphofructokinase in the red blood cells results in the breakdown of those cells and an increase in blood levels of bilirubin (a chemical found in red blood cells), although the person usually experiences no symptoms.

What causes phosphofructokinase deficiency?

Phosphofructokinase deficiency is caused by a genetic defect in the phosphofructokinase enzyme, which affects the breakdown of glucose (sugar). For more, see Causes/Inheritance.

What is the progression of phosphofructokinase deficiency?

The condition can begin anywhere from the teens to the 30s, and is not progressive, although weakness between episodes of exercise intolerance may occur late in the disease.

What is the status of research on phosphofructokinase 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.