Unusual presentation of primary cutaneous mucinosis with Blaschkoid Hemibody distribution: case report.

Primary cutaneous mucinosis (PCM) is a rare condition characterized by dermal mucin deposition without systemic disease, thyroid dysfunction, or paraproteinemia. The following report details the case of a 25-year-old female patient who exhibited the presence of firm, flesh-colored nodules and plaques that were strictly confined to the right hemibody, distributed linearly along Blaschko's lines. Laboratory tests revealed no significant findings, and histological analysis confirmed the presence of abundant dermal mucin, as indicated by Alcian Blue staining within a normal epidermis. This strictly unilateral Blachkoid distribution is exceptionally rare in mucinoses and raises the hypothesis of genetic mosaicism as a possible pathogenic mechanism. In contrast to generalized scleromyxedema, which carries systemic risk, this case exemplifies a localized, benign variant. This atypical presentation broadens the clinical spectrum of cutaneous mucinoses and underscores the significance of considering this diagnosis in atypical linear dermatoses.