An Atypical Presentation of Reticular Erythematous Mucinosis: A Case Report and Comprehensive Literature Review.

Reticular erythematous mucinosis (REM) is a rare form of primary cutaneous mucinosis, often linked to viral infections, inflammatory conditions, ultraviolet radiation, radiotherapy, malignant disorders, or an underlying immune dysfunction. It typically affects middle-aged women and manifests as symmetrical erythematous macules, papules, or plaques that exhibit a reticular and annular configuration, mainly on the midline of the thorax or dorsum. Although these regions represent the most prevalent sites, atypical occurrences have been noted. We report an unusual case of REM in a pediatric female patient with an ongoing history of B-cell acute lymphoblastic leukemia. The physical examination revealed an atypical distribution of REM lesions, symmetrically affecting the gluteal region and proximal thighs. Establishing a definitive diagnosis required a meticulous correlation between clinical, dermoscopic, and histopathologic findings. To our knowledge, this is the first documented case of REM in a patient with acute lymphoblastic leukemia. Our study underlines the importance of including REM in the differential diagnosis of persistent erythematous lesions, particularly in immunocompromised patients or those with a history of malignancy. Furthermore, we provide a comprehensive literature review, emphasizing the etiology, risk factors, pathogenetic mechanisms, diagnostic challenges, and different therapeutic options for REM.