Which skin condition is associated with the "herald patch"?

The skin condition associated with the "herald patch" is indeed pityriasis rosea. The herald patch is typically the first lesion to appear in this condition, presenting as a large, usually well-defined, oval or circular patch that is often pink or salmon-colored. This initial patch is often followed by the development of a more widespread rash characterized by smaller patches that typically align along the lines of skin tension, giving a distinctive appearance that can resemble a "Christmas tree" pattern.

Pityriasis rosea typically occurs in younger individuals and is believed to be of viral origin, although the exact cause remains unknown. The herald patch can help clinicians in diagnosing pityriasis rosea early, as it is a hallmark feature of the condition. Recognizing it is essential for differentiating pityriasis rosea from other dermatitis and skin infections that may have overlapping symptoms.