Which of the following disease occurs along Blaschko lines?
**Core Concept**
Blaschko lines are a pattern of skin lesions that follow the lines of Blaschko, which are determined by the migration and division of skin cells during embryonic development. These lines represent the path of proliferation and differentiation of the epidermal cells and are seen in various genetic disorders.
**Why the Correct Answer is Right**
Epidermal nevus syndrome (ENS) is a congenital condition characterized by the presence of skin lesions following Blaschko lines. The lesions in ENS are caused by the mutation of genes involved in the development and proliferation of skin cells. The condition can be associated with various systemic anomalies and is thought to result from the mosaicism of the affected gene.
**Why Each Wrong Option is Incorrect**
**Option A:** Vitiligo is an autoimmune condition characterized by the loss of pigment-producing cells, and while it can present in a segmental distribution, it does not follow Blaschko lines.
**Option B:** Psoriasis is a chronic inflammatory skin condition, but it does not follow Blaschko lines and is more commonly associated with the scalp, elbows, and knees.
**Option C:** Melanoma is a type of skin cancer, but it does not follow Blaschko lines and is more commonly associated with areas of sun-damaged skin.
**Clinical Pearl / High-Yield Fact**
Blaschko lines are a classic example of a dermatomal distribution, which can be seen in various genetic and acquired skin conditions. Remembering the lines of Blaschko can help you narrow down the differential diagnosis of skin lesions.
**Correct Answer: C. Epidermal nevus syndrome**