What phenomenon occurs when new skin lesions appear at sites of trauma?

Koebner's phenomenon is characterized by the appearance of new skin lesions at the site of trauma or injury to the skin. This response can occur in various skin conditions, most notably psoriasis, lichen planus, and vitiligo. When the skin is physically injured, it can trigger the immune system's response in susceptible individuals, leading to the formation of lesions in areas that have been traumatized, regardless of the underlying skin condition. This phenomenon illustrates the relationship between skin health and trauma, emphasizing that even minor injuries can promote the proliferation of certain skin diseases.

In contrast, the Leser-Trélat sign refers to a sudden eruption of multiple seborrheic keratoses and is often associated with internal malignancies. Darier's sign involves the formation of a wheal after stroking a lesion, typically related to mastocytosis, while rubeosis is the formation of new blood vessels in the iris, often related to diabetes or ocular ischemia, and does not involve skin lesion formation after trauma. This distinction highlights why Koebner's phenomenon specifically addresses new lesions at sites of trauma, making it the appropriate choice for this question.