Which condition presents with a herald patch and a Christmas-tree pattern?

Pityriasis rosea is characterized by the presence of a herald patch, which is a single, round or oval, pink to tan-colored lesion that typically appears first. This herald patch is followed by a "Christmas-tree" pattern of secondary smaller lesions that develop on the trunk and sometimes the extremities. The arrangement of these lesions on the skin resembles the branches of a Christmas tree, with the herald patch acting as the trunk.

Pityriasis rosea is a self-limiting condition often associated with viral infections, and it commonly affects younger individuals. Understanding the distinct features of this disease, such as the herald patch and the pattern of the rash, can help differentiate it from other skin conditions.