Hayes et al. (1987) described the first instance of a myopathy resulting from a defect in the malate-aspartate shuttle system. The patient was a 27-year-old man with a 3-year history of exercise-induced muscle pain, passage of red urine, ... Hayes et al. (1987) described the first instance of a myopathy resulting from a defect in the malate-aspartate shuttle system. The patient was a 27-year-old man with a 3-year history of exercise-induced muscle pain, passage of red urine, and elevated serum creatine kinase. The activity of the malate-aspartate shuttle was less than 20% of normal in the patient's isolated mitochondria. The parents, who were unrelated, showed no neurologic abnormality and had normal serum creatine kinase concentrations. There was no family history of neuromuscular disease. The patient had normal extraocular muscle function and no facial weakness but mild weakness of neck flexion. There was moderate symmetrical wasting affecting the deltoid, pectoralis major, supraspinatus, and infraspinatus muscles. He had mild weakness of the deltoid and infraspinatus muscles bilaterally and showed slight difficulty rising from a squatting position and from lying flat.