EXERCISE INTOLERANCE DUE TO MUSCULAR PHOS PHORYLASE-KINASE DEFICIENCY- CONTRIBUTION OF IN-VIVO METABOLISM INVESTIGATIONS

A 33 year old man has been presenting since childhood on exertional mu scle pain syndrome without myoglobinuria. Muscle biopsy revealed a vac uolar myopathy with glycogen excess in subsarcolemmal and intermyofibr illar spaces which was confirmed by electron microscopy. Plasma produc tion of ammonia was abnormally high during exercise on a bicycle ergom eter while the raise of lactate was normal. NMR spectroscopy showed an increased muscle glycogen content, with a slight and delayed drop of the pH during exercice. Phosphorylase b kinase activity was undetectab le in muscle specimen whereas activities of others enzymes of carbohyd rate metabolism were normal. Clinical presentation of our patient is c ompared to that of the reported cases of phosphorylase b kinase defici ency.