Anti‐ <scp>SAE</scp> Antibody–Positive Dermatomyositis Presenting With Widespread Erythema Complicated by Rosai‐Dorfman Disease

We report a rare case of dermatomyositis with positive anti-small ubiquitin-like modifier-1 activating enzyme antibody complicated by Rosai-Dorfman disease. A 41-year-old Japanese man presented with fever and general malaise, followed by developed progressive dysphagia. Physical examination revealed extensive erythema, along with characteristic heliotropic rash and erythematous keratotic plaques on the extremities. Laboratory examinations showed elevated muscle enzyme levels, and anti-small ubiquitin-like modifier-1 activating enzyme antibodies were detected by immunoprecipitation-Western blotting, whereas other myositis-specific autoantibodies were negative. Chest and abdominal computed tomography showed no findings suggestive of interstitial lung disease or internal malignancy, but revealed multiple painless lymphadenopathies in the inguinal regions. Lymph node biopsy revealed the diagnosis of Rosai-Dorfman disease. To the best of our knowledge, the present case is the first reported case of dermatomyositis associated with Rosai-Dorfman disease, which may suggest a shared immunopathological mechanism between the two diseases.