Myalgia in Patients with Dermatomyositis and Polymyositis Is Attributable to Fasciitis Rather Than Myositis: A Retrospective Study of 32 Patients who Underwent Histopathological Examinations

Objective. To determine the association between fasciitis and the clinical variables in patients with dermatomyositis (DM) and polymyositis (PM). Methods. We retrospectively reviewed the medical records of 32 patients (24 DM, 8 PM) with newly diagnosed DM and PM and in whom fascia and muscle specimens were histopathologically examined. The relationship between fasciitis and the clinical variables was statistically analyzed. These included age, sex, myalgia, muscle weakness, creatine kinase (CK) and aldolase activities, anti-Jo1 antibody, interstitial lung disease, and malignancy. Results. Twenty (62.5%) of the 32 patients who underwent the histopathological examination of a fascia specimen had fasciitis, including 18 (75%) of 24 patients with DM and 2 (25%) of 8 patients with PM. The frequency of fasciitis was significantly higher among the patients with DM than among the patients with PM (p < 0.05). Histopathologically, fasciitis in PM was very mild in comparison to that in DM. The frequency of myalgia in patients with fasciitis was significantly higher than that in patients without fasciitis (p < 0.05). However, myalgia was not associated with myositis. There were no significant differences in the patients with and without fasciitis in age, sex, manual muscle test 8 scores, CK or aldolase activities, or the presence of anti-Jo1 antibodies and malignancy. Conclusion. The frequency of fasciitis was significantly higher among patients with DM than among those with PM. Fasciitis, rather than myositis, was associated with myalgia.