CHRONIC PROGRESSIVE MYOPATHY WITH MYOGLOBINURIA: DEMONSTRATION OF A GLYCOGENOLYTIC DEFECT IN THE MUSCLE*

Abstract

Although little is known of the mletabolic dis- turbances in the various im-yopathies of manl and animals (1), in 1956, one of us (R. S.) observed a patient with a bizarre miiuscle disorder, associated with paroxysmal miivoglobiniuria, wlhose unusual clinical manifestations suggested a possible lead as to the nature of the mletabolic defect involved. In this patient, the most striking feature was his in- ability to perform miioderately severe mliuscular work even over slhort periods of timiie, wxhereas miiuscular activity of a minimal dlegree was toler- ated almnost without linlitatioins. For example, moderate exercise, suichl as climbing 10 steps of a stairway, produced severe an(d painiful cramps in the involved muscle groups, lastinig for approxi- mately an hour, and was followed by transient myoglobinuria. Contrariwise, slow walking on level ground was tolerated for houirs witlhout de- veloping craml-ps or eveni uniiduie fatigue. Mlore- over, it was found that dturing and followinig mod- erate exercise, which was sufficient to produce a cramp, the expected rise in blood lactate concen- tration (2-4) did not occur. These observations suggested that the )atient may suffer fronm a de- fect in glycogeinolysis, limiiting the enlergy avail- able for nmuscular contractioni to souirces other than anaerobic breakdown of glycogeni. This possibility was studied in viva and in vitro (5).