Clinically amyopathic dermatomyositis: clinical features, response to medications and malignancy-associated risk factors in a specific tertiary-care-centre cohort

Summary Background Clinically amyopathic dermatomyositis (CADM) is a subset of dermatomyositis (DM) characterized by the typical DM cutaneous manifestations but without myositis. There is a relative paucity of characterized cases of CADM in the peer‐reviewed medical literature. Objectives To characterize the clinical features, response to medications and malignancy‐associated risk factors of patients with CADM with available baseline data seen at a single tertiary‐care centre. Methods A retrospective review was undertaken of 44 patients with CADM with available clinical and serological data prior to onset of treatment. Results Patients with CADM comprised 18% of all patients with DM with baseline data available at our institution. Although the majority of patients showed improvement with the first prescribed treatment, most required additional medications to control their CADM. Six of 44 patients had an associated malignancy. Photosensitivity and periungual erythema were found to be associated with absence of malignancy (P = 0·03 and P = 0·02, respectively). Patients with malignancy‐associated CADM were found to be more likely to have a cutaneous response with the first prescribed treatment than patients without malignancy (P = 0·04). Conclusions CADM represents a significant subset of the DM population. As with classic DM, the cutaneous manifestations of CADM often represent a therapeutic challenge. A subset of patients with CADM has underlying malignancies, and these may differ from those typically associated with classic DM. Differences in serological abnormalities, cutaneous manifestations and response to first treatment among patients with CADM with and without malignancy were found, and suggest distinct pathophysiologies among CADM subsets. Characterization of this cohort expands the knowledge about this unique DM subset. What's already known about this topic? Clinically amyopathic dermatomyositis (CADM) comprises a significant subset of patients with dermatomyositis (DM). Like classic DM, CADM presents with similar cutaneous manifestations and may be associated with lung disease or malignancy. What does this study add? Although patients with CADM may initially respond to conservative therapy, most eventually require more aggressive treatment. Malignancies and clinical features found in patients with malignancy‐associated (MA)‐CADM may differ from those in MA classic DM. Clinical, serological and treatment response differences between patients with i