What condition is characterized by a solitary salmon-colored macule that evolves into smaller papules in a Christmas tree pattern?

Pityriasis rosea is characterized by a solitary salmon-colored macule, often referred to as a "herald patch," which is typically the initial lesion to appear. Following this, the condition progresses to the development of smaller oval papules that often exhibit a distinctive distribution pattern resembling the branches of a Christmas tree, particularly aligning along skin tension lines. This patterning is a hallmark of pityriasis rosea and helps differentiate it from other skin conditions.

The condition is considered self-limiting and usually resolves within several weeks to a few months without treatment. While its exact etiology is not completely understood, it is believed to be associated with viral infections, often linked to human herpesvirus 6 and 7.

Other conditions, such as eczema, psoriasis, and lichen planus, present with different features. Eczema typically presents as itchy, red, and inflamed patches rather than a single herald patch. Psoriasis usually appears as thick, silvery scales on well-defined plaques rather than the Christmas tree pattern seen in pityriasis rosea. Lichen planus has characteristic flat-topped purple papules that do not follow the same distribution pattern. Thus, the distinct presentation of the herald patch followed by a papular eruption in