Fishbein (1986) described the case of a 26-year-old military drill instructor in 'superb physical condition' who had experienced 3 brief episodes of severe, diffuse anterior chest pain after exercise during the previous 5 years. The chest pain was ... Fishbein (1986) described the case of a 26-year-old military drill instructor in 'superb physical condition' who had experienced 3 brief episodes of severe, diffuse anterior chest pain after exercise during the previous 5 years. The chest pain was at first considered cardiac in origin; after further studies, it was attributed to the metabolic myopathy of chest wall musculature. Using a clinical assay for the human erythrocyte lactate transporter and an ischemic exercise test suitable for evaluating muscle lactate transport, Fishbein (1986) demonstrated a deficiency of lactate transporter in both striated muscles and red blood cells from the patient. As a result, an acidic intracellular environment was created by muscle activity with consequent degeneration of muscle and release of myoglobin and creatine kinase. Fishbein (1986) noted that there are a number of enzymes which, although not essential for muscular activity, are important perquisites for maximal performance. One of these is myoadenylate deaminase (AMPD1; 102770). Fishbein (1986) referred to these enzymes as 'perquisitory' catalysts and suggested that defects in such catalysts may be expected to produce 'diseases of healthy people.' Most patients whose major complaint is of muscle pain or weakness are never identified with a specific disease or pathologic diagnosis. Fishbein et al. (1988) developed a physiologic assay for the human erythrocyte lactate transporter. With this test, the authors identified 8 males, aged 14 to 56 years, in good general health but with elevated serum creatine kinase levels and evidence of lactate transporter defect. Two patients had episodes of rhabdomyolysis and myoglobinuria after exercise, 3 had bouts of muscle cramping on exercise, 2 had such bouts as well as progressive muscle stiffness over 5 to 7 years, and 1 had minimal symptoms. The deficiency of enzyme was partial (50-75% loss) in all cases. Fishbein (1989) suggested that such defects may be a common cause of metabolic myopathy, fitness-failure, and postexertional rhabdomyolysis. Merezhinskaya et al. (2000) reported 5 unrelated males with subnormal erythrocyte lactate transport and symptoms and signs of muscle injury on exercise and heat exposure. One of the patients had previously been reported by Fishbein (1986). Clinical features included muscle cramping or stiffness, increased serum creatine kinase, normal EMG, and normal muscle biopsies. One patient demonstrated delayed lactate decline in exercised muscle.
In a patient with erythrocyte lactate transporter defect originally reported by Fishbein (1986), Merezhinskaya et al. (2000) identified a heterozygous mutation in the SLC16A1 gene (600682.0001). Two additional patients were found to be heterozygous for another SLC16A1 mutation ... In a patient with erythrocyte lactate transporter defect originally reported by Fishbein (1986), Merezhinskaya et al. (2000) identified a heterozygous mutation in the SLC16A1 gene (600682.0001). Two additional patients were found to be heterozygous for another SLC16A1 mutation (600682.0002). All 3 patients had erythrocyte lactate clearance rates that were 40 to 50% of normal control values. The authors suggested that homozygous individuals would be more severely compromised.