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.
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.
Phosphofructokinase deficiency is caused by a genetic defect in the phosphofructokinase enzyme, which affects the breakdown of glucose (sugar). For more, see Causes/Inheritance.
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.
Researchers on metabolic diseases of muscle are making progress on a number of fronts, including: