Blaschkoid Pityriasis Rosea on Trunk and Upper Limb of an Adult Male - A Case Report

Pityriasis rosea (PR) is a common self-limiting papulosquamous disorder, and its atypical variants, including the Blaschkoid type, are rare and may mimic other linear dermatoses, leading to diagnostic difficulty. We report an 18-year-old male who developed mildly pruritic erythematous papules and plaques arranged strictly along Blaschko’s lines on the right side of the trunk, upper arm, forearm, and palm, preceded by a herald patch. Histopathological examination was consistent with PR. A diagnosis of unilateral Blaschkoid PR was made, and the patient responded well to topical corticosteroids and antihistamines, achieving complete resolution within three weeks without relapse. This case highlights a rare unilateral Blaschkoid variant with simultaneous trunk and upper-limb involvement, emphasizing the importance of recognizing atypical presentations to avoid misdiagnosis and unnecessary interventions.