Via practica 5/2018
HyperCKemia – aetiology, clinical significance and differential diagnosis
Creatine kinase (CK) is one of the key enzymes of the energy cell system. CK catalyses the conversion of creatine and consumes adenosine triphosphate (ATP) to create phosphocreatine and adenosine diphosphate (ADP) and vice versa. Phosphocreatine serves as an energy reservoir, especially in active tissues. CK serum level is considered to be a sensitive laboratory parameter for neuromuscular diseases. However, there are several important causes of hyperCKemia unrelated to a recognized neuromuscular disease – strenuous muscle exercise, epileptic seizures, muscle injury, repeated intramuscular injection, surgery, medications (e.g. statins), toxins, viral infections, hypothyroidism, hypokalemia, malignant hyperthermia. The highest CK elevations are seen in rhabdomyolysis from any cause. In Duchenne and Becker muscular dystrophies, limb girdle muscular dystrophies and Miyoshi myopathy, the serum CK is markedly elevated in early stages but declines later on as the muscle mass is reduced. In polymyositis and dermatomyositis, the serum CK typically falls within weeks of starting corticosteroids but muscle weakness may take much longer to improve. Some muscle diseases do not cause an increase in CK, e.g. mitochondrial myopathies and some congenital myopathies. CK may be normal in some cases of two adult muscular dystrophies, namely facio-scapulo-humeral muscular dystrophy and myotonic dystrophy. It is important to remember that CK elevation occurs in anterior horn cell disorders such as amyotrophic lateral sclerosis, spinal muscular atrophy, bulbospinal muscular atrophy, and also in some neuropathies. Idiopathic asymptomatic hyperCKemia is a term used to describe the finding of an elevated serum CK concentration in the absence of symptoms that can be attributed to an underlying neuromuscular disease. All cases of asymptomatic hyperCKemia with no apparent medical explanation should undergo the assessment of acid α-glucosidase activity on dried blood spot. According to the results of some studies the selective screening in asymptomatic hyperCKemia allowed the identification of several Pompe patients in a pre-clinical stage. Muscle biopsy may be indicated in asymptomatic hyperCKemia if one or more of the following are present: the CK level is 3 or more times normal, electromyogram is myopathic or patients are < 25 years of age. In addition, women with CK 3 times over the normal may be offered DNA testing because of the possibility of carrying a dystrophin mutation.
Keywords: hyperCKemia, exogenous and endogenous causes, rhabdomyolysis, myopathies, muscular dystrophies, autoimmune myositis, anterior horn cell disorders, asymptomatic hyperCKemia
