Which condition involves congenital discoloration of a specific area of the skin due to pigmentation?

The condition that involves congenital discoloration of a specific area of the skin due to pigmentation is a nevus, commonly known as a mole. A nevus is usually present at birth or develops shortly after and can vary in color, size, and shape depending on the type of pigmentation. This localized area of varying pigmentation is a result of an accumulation of melanocytes, the cells responsible for producing melanin, which gives skin its color. Nevi can be benign, although some may require monitoring for changes that could indicate more serious conditions.

The other options represent different skin conditions that do not fit the description of congenital pigmentation. Vitiligo involves the loss of skin pigment leading to patchy discoloration but is not congenital. Melasma is characterized by brown or gray-brown patches on skin areas, typically associated with hormonal changes, rather than a congenital condition. Rosacea is a chronic inflammatory skin condition that causes redness and visible blood vessels, rather than a specific area of discoloration due to pigmentation.