Tc-99m pyrophosphate muscle labeling in McArdle syndrome.

This paper reports the findings on two patients with McArdle syndrome (myophosphorylase deficiency) in whom conventional bone scans with Tc-99m pyrophosphate revealed intense muscle labeling following exercise tests. The temporal pattern observed was similar to that seen with other types of muscle damage. The prolonged cramps often occurring with this entity appears to produce muscle damage that is readily demonstrable using conventional bone-scanning techniques.