Creatine kinase is an enzyme found in the heart, brain, and skeletal muscle. CK in the blood comes mainly from your muscles.
An elevated creatinine kinase can be suggestive of a variety of muscle disorders. Here are examples what some diseases that you may want to discuss with your personal physician.
Included in this group are motor neuron disease (amyotrophic lateral sclerosis), myasthenia gravis, the muscular dystrophies, and the various inherited, metabolic, drug–induced, endocrine, infectious and other inflammatory myopathies.
The muscle biopsy is a reasonable next step. You may also want to consider an EMG. Other considerations would be a rheumatology consult if the muscle biopsy is not revealing.
Other lab tests to consider are aldolase, lactate dehydrogenase, and the aminotransferase levels.
I am not familiar with the PMCR/AKCR abbreviations - it is possible that they are different terms from what I am familiar with.
Bibliography:
Miller. Clinical manifestations and diagnosis of adult dermatomyositis and polymyositis. UptoDate, 2004.