Definition - one of a group of muscle diseases that interfere with the processing of carbohydrates for energy production

Cause - a genetic defect in the phosphoglycerate kinase enzyme, which normally breaks down glucose (sugar) for energy production

Onset - infancy to early adulthood

Symptoms - may cause anemia, enlargement of the spleen, mental retardation and epilepsy (seizures); more rarely, weakness, exercise intolerance, muscle cramps and episodes of myoglobinuria (rust-colored urine indicating breakdown of muscle tissue)

Progression - muscle symptoms slowly progressive

Inheritance - X-linked recessive, meaning mostly affects males, although females are carriers

Facts About Metabolic Diseases