In a patient with dark spots on her face while taking oral contraceptives, what is the most likely diagnosis?

Melasma is characterized by the presence of dark, symmetric patches on the face, commonly occurring in women, and is often exacerbated by hormonal changes, such as those caused by oral contraceptives. This hyperpigmentation condition is linked to increased estrogen and progesterone levels, which can stimulate melanocyte activity—cells responsible for producing melanin, the pigment that gives skin its color. The typical presentation includes brown or gray-brown patches, primarily on the cheeks, forehead, nose, and upper lip.

In the context of a patient using oral contraceptives, the connection to melasma becomes particularly relevant. The hormonal influence of these medications can trigger or worsen pigmentation changes, making it the most likely diagnosis in this scenario.

While solar lentigo refers to age spots or "liver spots" resulting from sun exposure over time, it is not typically associated with hormonal changes or oral contraceptive use. Sunburn involves acute inflammation of the skin due to excessive UV exposure, which does not align with the chronic and often recurrent pattern of pigmentation observed in melasma. Lupus erythematosus can cause facial discoloration, but it usually presents with a characteristic butterfly rash and is often accompanied by systemic symptoms, which are not indicated in this case