The fluctuation of serum myoglobin levels in Duchenne muscular dystrophy and the carrier.

The diurnal changes of serum myoglobin level and CK activity were investigated in 20 cases of Duchenne dystrophy and 6 normal males under ordinary circumstances in their daily lives. Changes of myoglobin levels were also checked in 25 cases of Duchenne carrier and 11 control females with muscular exercise by ergometer of 70 W for 3 min. In Duchenne dystrophy, the myoglobin level was rather low before waking up, then it abruptly increased thereafter and remained high until retiring. The fluctuation range of myoglobin was greater than that of CK. The myoglobin level of control males was extremely low compared with that in Duchenne dystrophy. In Duchenne carriers, although CK activity did not significantly change after the exercise, 5 of 11 known carriers showed an increased myoglobin level.