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Introduction
Creatine kinase (CK) is an enzyme which catalyzes the reaction of creatine and adenosine triphosphate to create phosphocreatine and adenosine diphosphate. The three isoenzymes involved are CK-MM, which is mainly present in skeletal muscle; CK-MB in cardiac muscle and CK-BB which is predominantly expressed in the brain. The sum of these three isoenzymes quantifies the total serum CK (sCK) levels (1,2). CK levels have been reported based on age, ethnicity and gender and can be stratified in a ‘high CK’ group among men of African descent with a mean CK value of 237.8 U/l, an ‘intermediate CK’ group comprising of non-African-American men and women with mean CK levels between 109.3 and 149.7 U/l and a ‘low CK’ group consisting of Caucasian women with mean CK levels between 64.6 and 79.8 U/l (3). Recent European Federation of Neurological Society (EFNS) guidelines recommended that hyperCKemia should be redefined as sCK >1.5 fold the upper limit of normal (4), according to a 97.5% threshold and normal values introduced by Brewster et al (5) for both genders of African and Caucasian descent.
CK measurement represents a usual laboratory parameter as a part of routine follow-up in the daily practice or to assess patients complaining of muscle-related symptoms. sCK (phospho) level elevation sometimes represents an incidental laboratory finding leading to a diagnostic enigma as it can be related to a variety of disorders such as those of neuromuscular, cardiac, metabolic, endocrine and traumatic origin (2,4,6). Other clinical situations that can lead to hyperCKemia include viral infections, toxin accumulation, heavy muscle exercise, surgery, pregnancy, obstructive sleep apnoea, neuroacanthocytosis syndromes, macro-CK, malignant hyperthermia syndrome and medications (4,6). However, elevated CK levels may be observed rarely among asymptomatic individuals.
We present a case of asymptomatic idiopathic hyperCKemia with such extremely high levels of CK as to be of the very few internationally reported and, to the best of our knowledge, the first case reported from a rural primary care setting in Greece. Thus, we carried out a literature overview by discussing this condition.
Case presentation
Informed consent was obtained from the patient for publication of this case report. A Caucasian...