Background and design: We retrospectively studied 12 patients with dermatomyositis (DM) with at least one laboratory criterion of muscle involvement but without muscle weakness. We reported their outcome without systemic corticosteroid treatment and searched for distinctive baseline data and associated neoplasia among a group of 29 patients with classic DM.
Results: After a mean follow-up of 5.3 years, complete or partial skin improvement occurred in nine patients with DM without muscle weakness, and muscle enzyme levels were normalized in all. When compared with the classic DM group, no statistical differences were found for associated neoplasia or for any baseline data studied except, as expected, for muscle parameters.
Conclusions: The lack of distinctive baseline data between DM without muscle weakness and classic DM suggests that there is a continuum from amyopathic to classic DM. However, DM without muscle weakness is a clinical entity with respect to favorable long-term prognosis. Unless frank muscle weakness develops, treatment with systemic corticosteroids can be avoided.