An increased level of serum creatine kinase has been considered as an indirect sign of muscular disorders but it may be an indicator of other diseases (malignant hyperthermia, tumors or endocrinopathy). Some patients present with a stationary clinical condition and absence of muscular symptoms, in whom the unique abnormality is hyperCKemia that is not associated with any biological or genetic diagnosis of MD. In others asymptomatic patients, an increase in CK may be a hematological marker that can predict muscular disease. In this article, we review the causes that can lead to transitory or persistent HC.