Pityriasis Rosea with Herald Patch MCQ — NEET PG Practice Question | NEETPGAI
Pityriasis Rosea with Herald Patch
medium
hand Dermatology
A 22-year-old woman presents with a 10-day history of a solitary 4 cm pink, oval, scaly patch on her left flank, followed 4 days later by a sudden generalized eruption of smaller similar lesions on the trunk and proximal extremities. The structure marked **A** in the diagram represents the initial lesion. Which of the following clinical features of the structure marked **A** is MOST important in distinguishing this condition from tinea corporis and secondary syphilis?
A. Involvement of the trunk with relative sparing of palms, soles, and face
B. Presence of a collarette scale with trailing active border
C. Solitary larger lesion preceding the generalized eruption by several days
D. Oval morphology with orientation along Langer skin tension lines
Explanation
Why "Solitary larger lesion preceding the generalized eruption by several days" is right
The herald patch (structure A) is the pathognomonic early lesion of pityriasis rosea. Its defining feature is that it appears FIRST and ALONE, followed days to weeks later by a generalized secondary eruption of smaller lesions. This temporal sequence—a solitary larger patch preceding the rash—is the single most distinguishing morphologic clue that differentiates pityriasis rosea from its major mimics. Tinea corporis does not present with a herald patch; lesions are typically multiple and simultaneous. Secondary syphilis presents with synchronous lesions and crucially involves the palms and soles, which pityriasis rosea spares. The herald patch's solitary, antecedent nature is the key diagnostic feature (Drago F. Pityriasis rosea. JAAD. 2023; BAD guidance 2022).
Why each distractor is wrong
Presence of a collarette scale with trailing active border: While the collarette scale (structure D) is characteristic of pityriasis rosea and helps confirm the diagnosis once the rash is established, it is NOT the distinguishing feature that separates pityriasis rosea from its mimics. Tinea corporis also has a trailing scale; secondary syphilis can show scaling. The collarette alone does not explain why a single lesion preceded the eruption.
Oval morphology with orientation along Langer skin tension lines: Oval lesions aligned with skin tension lines (structures B and C) produce the classic Christmas-tree pattern and are typical of pityriasis rosea, but these features appear in the SECONDARY eruption, not the herald patch alone. This does not explain the temporal sequence that distinguishes pityriasis rosea from tinea corporis (which lacks a herald phase) or secondary syphilis (which is synchronous).
Involvement of the trunk with relative sparing of palms, soles, and face: This distribution pattern is indeed characteristic of pityriasis rosea and helps rule out secondary syphilis (which involves palms and soles). However, this describes the OVERALL distribution of the secondary eruption, not the specific distinguishing feature of the herald patch (A) itself. The question asks what about structure A is most important in the differential diagnosis.
High-YieldNEET PG
The herald patch—a solitary, larger lesion appearing days before the generalized eruption—is the pathognomonic early sign of pityriasis rosea and is absent in tinea corporis and secondary syphilis.
Drago F. Pityriasis rosea. JAAD. 2023 review; BAD pityriasis rosea guidance 2022
Practice similar questions
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.
