I am working up a man with a slowly progressive (over 5 years) axonal neuropathy with some 'red flag' features (asymmetry, non-length dependent) and have discovered he has an elevated CK (2.5 x ULN) which has remained elevated despite stopping his statin therapy and abstaining from exercise prior to testing.
Neuropathy is often listed as a possible cause in guidelines on assessment of 'asymptomatic hyperCKemia', but I can't find any guideline on how high one would expect the CK to be due to this cause. He has minimal motor involvement both clinically and on NCS. His needle EMG was limited to deltoids and showed possible mild myopathy changes (short duration, early recruitment) without inflammatory features.
His chief complaint is of pain and numbess, so wondering how to decide on the utility of muscle biopsy and/or additional blood work looking for myopathic disorders.
Any advice or references for my own reading much appreciated.