Ischemic exercise test: failure to detect partial expression of McArdle's disease.
The forearm ischemic exercise test (FIET) is a very important clinical tool for evaluation of patients suspected to have a metabolic disorder of muscle function. Failure to elevate lactate in blood washed out from ischemically exercised muscles confirms an abnormality of glycolytic metabolism. A normal increase of lactate on FIET is assumed to rule out a disorder of glycolytic metabolism. Two patients with low levels of muscle phosphorylase are presented who produced a normal elevation of lactate on FIET. This suggests that, although the FIET is capable of identifying patients with absence of myophosphorylase, the test cannot identify patients with a partial expression of that disorder. Evaluation of the blood samples for ammonia in addition to lactate can be a significant help in confirming that the exercise performed by the patient was an adequate challenge for the glycolytic pathway. In addition, failure to elevate ammonia on ischemic exercise can identify a relatively new disorder of muscle metabolism.
D000328:Adult; D005080:Exercise Test; D005260:Female; D005542:Forearm; D006008:Glycogen Storage Disease / Q000503:physiopathology*; D006012:Glycogen Storage Disease Type V / Q000503:physiopathology*; D006019:Glycolysis; D006801:Humans; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008875:Middle Aged; D009132:Muscles / Q000098:blood supply / Q000201:enzymology / Q000503:physiopathology*; D010641:Phenotype; D006005:Phosphorylases / Q000378:metabolism
D007773:Lactates; D019344:Lactic Acid; D006005:Phosphorylases