Key clinical point: The prevalence of dermatomyositis without dermatitis among patients with biopsy-confirmed dermatomyositis was approximately 8% in a Japanese study. Dermatomyositis sine dermatitis was significantly associated with anti–nuclear matrix protein 2 (anti-NXP-2) autoantibodies.

Major finding: Anti-NXP-2 autoantibodies were detected in 86% of the patients without a rash at the time of biopsy, compared with 28% of the patients with rashes.

Study details: A cohort study of 182 patients with dermatomyositis who had myxovirus resistance protein A expression in myofibers on muscle biopsy and were tested for dermatomyositis-specific autoantibodies.

Disclosures: The study was supported by an intramural research grant of the National Center of Neurology and Psychiatry and a grant from the Japan Society for the Promotion of Science. The authors disclosed personal fees from pharmaceutical companies and government and corporate grants outside the submitted work.