Edema localized to the lips as a novel manifestation of myositis

Polymyositis (PM) and dermatomyositis (DM) are idiopathic inflammatory myopathies with presumed autoimmune pathogenesis, characterized by the features of proximal skeletal muscle weakness and evidence of muscle inflammation. Skin manifestations usually prompt earlier recognition and diagnosis of DM than PM, which has no rash. Associated delayed diagnosis and treatment in PM lead to worse outcomes. Therefore, an accumulation of case reports regarding initial symptoms suggestive of PM has been required to obtain an earlier diagnosis and better clinical outcomes in PM patients. We herein report a PM patient with an unusual presentation of edema restricted to the lips, which was clinically suggestive of granulomatous cheilitis but histologically verified as a manifestation of myositis. In this patient, no myositis-specific antibodies including anti-nuclear matrix protein 2 antibodies, were detected, and histological analysis on the muscle biopsy specimen revealed CD4-dominant lymphocyte infiltration but no C5b-9 deposition nor myxovirus resistance protein A expression. Further analysis with MRI (magnetic resonance imaging) scan of the lips showed increased signal intensity in the muscle layer on short TI inversion recovery images, and these suggest the potential of MRI as a useful tool for exploring the inflammatory site and the possibility of myositis in swollen lips. Thus, our report indicates the importance of suspecting myositis in the case of unusual edema restricted to the lips.