What type of skin disorder is characterized by increased pigmentation of the skin?

Hyperpigmentation is the correct answer as it specifically refers to an overproduction of melanin in certain areas of the skin, leading to darker patches. This increased pigmentation can be caused by a variety of factors, including sun exposure, hormonal changes, certain medications, and skin injuries. Conditions such as melasma and age spots are common examples of hyperpigmentation.

In contrast, hypopigmentation involves a reduction in melanin, resulting in lighter skin areas. Dermatitis encompasses a range of inflammatory skin conditions, which may not directly involve changes in pigmentation, and atrophy refers to the thinning or loss of skin, which can occur due to various reasons but is not characterized by increased pigmentation. Understanding these distinctions is important for accurately diagnosing and treating skin conditions.