Clinical and experimental observations have established that damaged or degenerating muscles will release its contents, particularly enzymes, into the general circulation, and that this process can be measured by an increase in the level of certain enzymes in the serum. Assay of serum enzymes in the assessment of muscle disease has been employed most widely in the study of muscular dystrophy both to establish the diagnosis early1,2 and to discover maternal carriers of the sex-linked form.3,4 However, it is clear that at least some muscle enzymes are released into serum by other myopathies, particularly acute myositis,5,6 and even by neurogenic atrophy.5,6
That the source of the serum enzymes is indeed the muscle has been established by a number of findings. Dreyfus et al7 showed that the venous aldolase level was sometimes slightly higher than the arterial aldolase in cases of muscular dystrophy. The isoenzymes of