Pulmonary gas exchange during exercise and muscular glycogen storage disease.

Background.- The diagnosis of muscular glycogen storage disease is usually difficult to demonstrate as symptoms normally consist of muscular cramps an d exercise intolerance. Informations obtained from the study of the pulmona ry gas exchange during exercise in a young patient with a glycogen storage disease are reported. Case report. - The ventilatory and gas exchange responses to a cyclo-ergome ter exercise were studied in a 17-year-old girl during a ramp-like test (5 W/min). The temporal profile of CO2 production (V over dot CO2) response wa s clearly abnormal: V over dot CO2 was always lower than oxygen consumption throughout the test, reflecting the lack of lactate buffering by the bicar bonates due to the absence of lactate production. The respiratory ratio was still around 0.75 at the peak of the test. In contrast, responses were per fectly normal in the other members of the family, allowing rejection of the diagnosis of glycogen storage disease without any blood sampling. Conclusion. - This case illustrates the benefit of studying pulmonary gas e xchange during exercise for a non-invasive diagnosis of muscular glycogen s torage disease and detection of the disease in the other members of family. (C) 1999 Elsevier, Paris.