Which description best characterizes the rash distribution in pityriasis rosea?

• A. Vesicular lesions on the trunk with collarette scaling
• B. Christmas tree pattern on the trunk with collarette scaling
• C. Pustular acneiform lesions on the face
• D. Annular distribution around the body

Answer: (B)

Pityriasis rosea shows oval patches that appear on the trunk and spread along the skin’s cleavage lines, producing a Christmas tree–like arrangement down the trunk. Each patch has collarette scaling, meaning a fine ring of scales at the outer edge that trails inward toward the center. This combination—trunk-dominant distribution following skin lines with a trailing edge of scale—is classic for the condition. The other descriptions don’t fit because pityriasis rosea lesions are not primarily vesicular or pustular and don’t form a simple annular pattern; the distinctive trunk-centered, line-following pattern with collarette scaling is the hallmark.