Dermatomyositis is an inflammatory myopathy of unknown cause accompanied by a characteristic cutaneous eruption. Despite the frequently debilitating severity of the skin involvement, most studies have focused on the muscle disease and no controlled studies have been done to study systematically the skin disease in dermatomyositis or its treatment. This is in part due to the lack of standard methods for evaluating the skin involvement of dermatomyositis. Validated measures that can be used to judge the severity of skin involvement of patients with dermatomyositis and to evaluate and compare different therapies are not available yet. The purpose of this study is to validate a dermatomyositis skin disease severity measure (DSSI) developed based on the Psoriasis Area and Severity Index (PASI), to determine the clinical significance of changes in the DSSI, and to collect data on the expected effect size and variability of two common treatments. The hypothesis is that a modified version of the psoriasis severity measure can be used to accurately measure the severity of skin disease in patients with dermatomyositis. The successful completion of the study will permit future studies that assess the effectiveness of different treatments for dermatomyositis skin disease and provide data that could be used for power analysis calculations for designing future full-scale studies.
