Characteristics of Patients With Adult-Onset Dermatomyositis at 2 Tertiary Care Centres in Ontario, Canada

Dermatomyositis (DM) is an idiopathic inflammatory myopathy characterized by progressive muscle weakness and distinctive cutaneous findings. The exact incidence and prevalence of DM in the general population is largely unknown, and data on demographic and clinical features in patients in Canada are lacking. This study aimed to comprehensively evaluate the patients with DM in Southwestern Ontario, Canada. A retrospective chart review was conducted for patients with adult-onset DM at 2 tertiary care centres in Ontario, Canada, over a 13 year period. One hundred fourteen patients were included. The mean age was 59, and 80% of patients were female. Skin and muscle involvement coincided in 63% of patients, while skin predated muscle involvement in 11%. Most common characteristic skin manifestations included Gottron's papules (69%), Heliotrope sign (66%), V sign (61%), and Shawl sign (56%). Among the 114 patients, 88 (77%) were myopathic while 26/114 (23%) were clinically amyopathic dermatomyositis. In the myopathic type, upper extremity weakness, lower extremity weakness, and dysphagia were present in 87%, 81%, and 29% of patients, respectively. Elevated creatine kinase, C-reactive protein, lactate dehydrogenase, and erythrocyte sedimentation rate were found in 66%, 35%, 33%, and 32%, respectively. Lung disease was reported in 39%, particularly interstitial lung disease. Other associated features included malignancy, cardiovascular disease, and less commonly gastrointestinal disease. DM is a multifaceted autoimmune disease with distinct cutaneous and muscular findings. Our study results align with the growing body of evidence supporting DM as a complex systemic disease with the potential involvement of other organs such as the pulmonary, cardiovascular, and gastrointestinal systems.