341 A longitudinal study of cutaneous dermatomyositis

Abstract

Prior studies have described the course of dermatomyositis (DM) using muscle weakness and enzymes; however, limited studies have described the course of cutaneous disease. A retrospective cohort included patients 18 years or older with clinical or histologic evidence of DM who had the Cutaneous Dermatomyositis Disease Area and Severity Index (CDASI) activity subscore recorded for at least 2 years. Disease progression was classified into improved, worsened, or stable based on net area under the curve per unit time relative to baseline CDASI score and a fitted linear slope. Disease course was classified into monophasic, polyphasic, or chronic based on definitions in the literature. Subjects were divided into mild and moderate-severe (MS) baseline severity groups and outcome measures were compared. In our cohort of 40 DM patients, the majority were female (90%) and Caucasian (95%), with a mean age of 52.9 years at baseline. Disease subtype was classified as classic (52.5%) and skin predominant (47.5%). Mean follow-up time was 3.50 years (SD=1.0). More patients had MS disease at baseline (N=24, 60%) compared to mild disease (N=16, 40%). Average disease activity was significantly different between the mild and MS groups (9.10 vs. 14.96; P = 0.004). The majority of DM patients showed an improvement in disease activity (N=23, 57.5%) compared to a worsening (N=8, 20%) and stable (N=9, 22.5%) progression. Within the mild group, a majority of the patients’ disease activity remained stable (N=8, 50%) compared to improvement in the MS group (N=20, 83%). Most DM patients had a polyphasic course (N=33, 82.5%) compared to monophasic (N=5, 12.5%) and chronic (N=2, 5%) courses. Variability in disease activity over time (average flares/yr) was independent of baseline disease activity. In summary, the majority of our patients had MS disease activity at baseline that improved with a polyphasic course while fewer had mild baseline disease that mostly remained stable with a polyphasic course.