Myalgia during interferon therapy--does it warrant monitoring muscle enzymes?

Myositis during interferon therapy is a known but rare adverse event. However the clinician may overlook the symptom-complex of proximal muscle weakness and myalgia, seen in myositis, since myalgia is a commonly reported side effect of therapy. In this context then, is there a role for monitoring muscle enzymes to detect subclinical myositis in patients on interferon therapy? We prospectively monitored the creatine kinase (CK) and lactate dehydrogenase (LD) levels in all our patients who reported myalgia during treatment and noted that muscle enzymes remained within normal range throughout the duration of treatment. This excluded the possibility of subclinical myositis in myalgic patients and thus led us to conclude that routine monitoring of muscles enzymes is neither necessary nor beneficial.