Okay, let's tackle this question. The question is about when a salmon patch usually disappears. First, I need to recall what a salmon patch is. From what I remember, salmon patches are a type of vascular birthmark. They're also called nevus simplex. Common locations are the nape of the neck, eyelids, or the forehead. They're pink or red, flat, and look like salmon flesh, hence the name.

Now, the question is about the age by which they disappear. I think salmon patches are usually transient. Some sources say they fade over time. But wait, do they disappear completely or just fade? I need to check the typical timeline. I recall that infantile hemangiomas are different; they grow and then regress, often by school age. But salmon patches are capillary malformations, not hemangiomas. So maybe they don't regress as much. Wait, but some sources mention that salmon patches can fade, especially if they're on the nape (called a stork bite). The ones on the face might persist longer. Hmm.

Wait, the key here is the age. If the question is about when they disappear, the answer might be by a certain age. I think the common teaching is that salmon patches (stork bites) on the nape typically fade by age 1-2 years. But if they're on the face, like the eyelid, they might persist into adulthood. So the answer depends on the location. But the question is general, not specifying location. Maybe the standard answer is that they disappear by age 1-2 years. Let me verify. A quick check in my notes: Salmon patches (nevus simplex) are common in newborns, often on the nape, and they usually fade within the first year or two. So the correct answer would be around 1-2 years. So the options might have something like 1 year or 2 years. But the options here are A, B, C, D. The correct answer given by the user is missing, but the correct answer is probably an age like 1 year or 2 years. Let me make sure. The user's correct answer is probably option B: 1 year or option C: 2 years. Let me think. If the options are A. 6 months, B. 1 year, C. 2 years, D. 5 years. Then the correct answer would be C: 2 years. So in the explanation, the core concept is that salmon patches are capillary malformations that typically fade by age 1-2 years. The mechanism is that they are superficial, so they fade with age. The incorrect options would be other ages where they don't disappear. The clinical pearl is to differentiate from hemangiomas, which grow and then regress later. So the answer is 2 years.

**Core Concept**
Salmon patches (nevus simplex or stork bites) are superficial capillary malformations common in newborns. They result from dilated capillaries in the upper dermis and typically fade with age due to vascular maturation.

**Why the Correct Answer is Right**
Salmon patches located on the nape of the neck usually disappear by age **2 years**. These lesions are composed of thin-walled capillaries that gradually involute as the vascular system matures. Facial salmon

✓ Correct Answer: B. One year