Exploring the landscape of flagellate erythema as a rare cutaneous symptom of idiopathic inflammatory myopathy: a case series-based review.

Abstract

Flagellate erythema is an exceptionally rare cutaneous manifestation of idiopathic inflammatory myopathies (IIM) with poorly understood clinical significance. We report two patients who developed zebra-like flagellate erythema: one with immune-mediated necrotising myopathy (IMNM) and one with anti-Mi-2-positive cancer-associated myositis (CAM). To place these observations in broader context, we performed a thorough literature search across PubMed, Scopus and Embase and identified 34 previously published cases of IIM-associated flagellate erythema. The most frequent underlying diagnosis was dermatomyositis (n = 14, 41.2%), followed by CAM (n = 9, 26.5%), amyopathic/clinically amyopathic dermatomyositis (n = 6, 17.6%), and juvenile dermatomyositis (n = 5, 14.7%). Anti-TIF1-γ antibodies were identified in 6 of 34 patients (17.6%) and anti-MDA5 antibodies in 7 of 34 (20.6%); malignancy was reported in 9 of 34 (26.5%), while a substantial proportion of cases were seronegative or lacked antibody testing. Muscle weakness or myalgia was present in most of the combined cohort, and a fatal outcome was reported in approximately one-fifth of cases. Our cases expand the clinical and serological spectrum of myositis-associated flagellate erythema, including the first report of this presentation in IMNM. While flagellate erythema has most often been reported with CAM or anti-TIF1-γ antibodies, the literature remains inconsistent, and current case-report-based evidence does not support a definitive association with any single serological or clinical subgroup. In our patients, flagellate erythema coincided with disease exacerbation; although this should be interpreted cautiously given the limited evidence, its occurrence may warrant careful evaluation for IIM flare and, where appropriate, malignancy screening.