Dermatomyositis — SCE Rheumatology MCQ

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ModerateAutoimmune SerologyDermatomyositisSCE Rheumatology

A 42-year-old woman presents with symmetrical proximal muscle weakness, a creatine kinase concentration of 4200 U/L, a V-sign rash over the anterior chest and a shawl-sign rash over the upper back and shoulders. Anti-Mi-2 antibodies are detected. Which clinical course is most strongly associated with this autoantibody?

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Correct answer: E — Favourable treatment response and overall prognosis

Anti-Mi-2 antibodies define a classic dermatomyositis phenotype with prominent muscle disease and characteristic cutaneous signs, including V-sign and shawl-sign erythema. Cohort studies associate anti-Mi-2 positivity with a good response to immunosuppressive treatment, frequent remission and generally favourable survival, making A the best answer. Rapidly progressive interstitial lung disease is characteristically associated with anti-MDA5 antibodies, while a strong malignancy association is most characteristic of anti-TIF1-gamma. Inclusion body myositis is a distinct clinicopathological disorder and does not represent the expected evolution of anti-Mi-2-positive dermatomyositis. Rituximab may be used for refractory inflammatory myopathy, but anti-Mi-2 positivity does not itself predict treatment resistance or a requirement for rituximab. Anti-Mi-2 status should not, by itself, replace appropriate malignancy assessment in adult-onset dermatomyositis.

Reference: Liang L et al. Anti-Mi-2 antibodies characterize a distinct clinical subset of dermatomyositis with favourable prognosis. European Journal of Dermatology. 2020. https://pubmed.ncbi.nlm.nih.gov/32293565/