Melasma is characterized by which symptom?

Melasma is primarily characterized by brownish pigmentation on the face, which aligns with the correct answer. It presents as dark, discolored patches typically found on areas of the skin that are frequently exposed to the sun, such as the cheeks, forehead, and upper lip. This condition is influenced by factors like sun exposure, hormonal changes (such as those occurring during pregnancy or with the use of birth control), and genetic predisposition.

In contrast, the other symptoms listed do not pertain to melasma. Increased appetite is not a symptom associated with skin conditions and is more related to metabolic or psychological factors. Darkened skin on the neck could relate to various conditions, including acanthosis nigricans or other skin disorders but does not define melasma. Swelling in the limbs is typically indicative of edema or other systemic conditions, which is unrelated to the pigmentation changes seen in melasma. Thus, the characteristic brownish pigmentation specifically on the face aptly captures the defining nature of this condition.