What skin condition is characterized by a herald patch and a Christmas tree pattern?

Pityriasis rosea is known for its distinctive features, including the presence of a herald patch, which is typically a single, large, oval lesion that appears on the skin before a generalized rash develops. This herald patch usually precedes a more widespread eruption of smaller lesions that flourish along skin lines, resembling a Christmas tree pattern when viewed on the back. The arrangement of these lesions in a descending pattern, combined with the initial presentation of the herald patch, is a hallmark of Pityriasis rosea.

In contrast, psoriasis is characterized by raised, scaly plaques, often found on the elbows, knees, and scalp, and does not exhibit a herald patch or the Christmas tree distribution. Contact dermatitis primarily presents with localized inflammatory reactions to allergens or irritants and lacks the herald patch and pattern associated with Pityriasis rosea. Eczema is a broader term that encompasses various types of dermatitis, typically presenting with itchy, inflamed skin but also without the herald patch or distinct rash distribution seen in Pityriasis rosea.