Flagellate erythema in anti‐ MDA5 ‐positive dermatomyositis

A 29-year-old man presented with a 1-month history of intermittent fever and pruritic rash. Examination showed well-demarcated flagellate erythema with hyperpigmentation on the back (Figure 1). Histopathology revealed parakeratosis and scattered necrotic keratinocytes in the epidermis, with perivascular lymphocytic and neutrophilic infiltrates in the upper dermis. Further autoimmune survey showed positive anti-melanoma differentiation-associated protein 5 (MDA5) antibodies (++) and markedly elevated ferritin (3096 ng/mL). Following a rheumatology consultation, the patient was diagnosed with anti-MDA5-positive clinically amyopathic dermatomyositis. The patient was treated with systemic prednisolone (15 mg/day), leading to complete resolution of the rash and fever. Flagellate erythema is a distinctive cutaneous eruption characterized by parallel linear or curvilinear erythema resembling flagellation. It is associated with shiitake dermatitis, adult-onset Still's disease, chemotherapy, and dermatomyositis. Recognition of this distinctive pattern should prompt evaluation for anti-MDA5 disease, a subtype frequently lacking muscle involvement yet associated with rapidly progressive interstitial lung disease and high mortality. The authors would like to thank Dr. Hao-Kai Chuang for the diligent collection of clinical data. This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors. None to declare. The study was reviewed and approved by an institutional review board or ethics committee at participating centres. The study was conducted in accordance with the Declaration of Helsinki and adhered to Good Clinical Practice guidelines. The patient in this manuscript has given written informed consent to publication of his case details. Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.