What are cafe au lait spots characterized by?

Cafe au lait spots are characteristic areas of increased melanin in the skin that appear as pale brown or tan macules or patches. These spots typically have a smooth border and can range in size. They are commonly associated with certain genetic conditions, such as neurofibromatosis, but can also occur in individuals without underlying health issues. Their name, which means "coffee with milk" in French, reflects their light brown color.

The other options describe different skin characteristics that do not apply to cafe au lait spots. Bright red lumps on the skin, for example, could refer to cherry angiomas or other types of vascular lesions, while swelling from fluid accumulation would indicate edema, and dark blue or purple patches might suggest bruising or conditions like ecchymosis. Thus, the defining feature of cafe au lait spots being areas of increased melanin that appear pale brown stands out as the accurate description.