Physiologic assessment of phosphoglycerate mutase deficiency: incremental exercise test
Kissel, J.T.; Beam, W.; Bresolin, N.; Gibbons, G.; Dimauro, S.; Mendell, J.R.
Neurology 35(6): 828-833
1985
ISSN/ISBN: 0028-3878 PMID: 2987758 Document Number: 261463
A 3rd case of phosphoglycerate mutase (PGAM) deficiency, a metabolic myopathy involving terminal glycolysis, was identified in a 24-yr-old black man with episodic, exercise-induced myoglobinuria since age 13. To better understand the physiologic consequences of PGAM deficiency, incremental exercise testing was performed. Results were compared with those of 2 patients having myophosphorylase deficiency and 5 normals. In contrast to the patients with phosphorylase deficiency, the PGAM-deficient patient achieved near-normal levels of maximal exercise and produced a normal peak lactate after exercise. The mechanisms underlying the asymptomatic performance of such strenuous exercise in this case are uncertain, but unidentified factors may be operative in precipitating attacks of myoglobinuria in patients with some metabolic myopathies. Despite similar clinical histories, patients with different glycolytic enzyme deficiencies can have striking differences in exercise tolerance.