Researchers at Children’s Hospital Boston, MA, have shown a linear relationship between serum CPK and serum ALT and AST and a logarithmic relationship between serum enzyme levels and age for boys with Duchenne (n=46) or Becker (n=9) muscular dystrophy (DMD or BMD). A mathematical model to predict serum ALT and AST levels with known CPK and age was developed to provide reassurance that elevated transaminase may be indicative of muscle disease, avoiding unnecessary tests of liver dysfunction. Serum transaminase was highest in ambulant boys with DMD (1220 U/L ALT and 801 U/L AST). These levels were 22 and 12 times higher than upper limit nomal levels for ALT and AST, respectively. The study was prompted by the observed reluctance of clinicians to attribute high transaminase levels to muscle disease, leading to delayed diagnosis and extensive tests for liver dysfunction. 
COMMENT. High serum transaminase levels should alert clinicians to possible muscle disease and prompt serum CPK estimation when clinically indicated. Unnecessary liver function tests and withdrawal of drug therapy may be avoided.