INTRODUCTION
Dyschromia is one of the most common reasons for patients to seek dermatological care, especially among individuals with skin of color.1,2 The majority of cases present as melasma or post-inflammatory hyperpigmentation (PIH),3,4 acquired hyperpigmentation disorders that most frequently affect patients with darker skin types (Fitzpatrick III-VI).4-7 Melasma is seen more often in reproductive-aged female or adult patients,5,6 whereas PIH can affect male or female patients of any age.4,7 Melasma and PIH can negatively impact quality of life.8,9
MATERIALS AND METHODS
Presentation and Diagnosis
Melasma and PIH present as pigmented macules and patches most often located on the face.1,7 In melasma, these symmetric, brown-to-gray pigmented areas occur mainly on sun-exposed skin.7 With PIH, pigmented areas are irregular/non-symmetric and may not be limited to sun-exposed skin; lesions range from light brown to dark gray/black in color and tend to occur at the site of cutaneous injury or inflammation.4 The color of melasma and PIH lesions varies depending on the cutaneous depth of the pigmentation alterations.4,7
Melasma and PIH are diagnosed clinically, though Wood’s lamp evaluation, dermoscopy, or biopsy can confirm the diagnosis or determine the depth of pigment deposition (ie, epidermal, dermal, mixed, or indeterminate [melasma]; dermal versus epidermal [PIH]).4,7 Pigmentation depth can affect treatment choices, as dermal melasma and PIH are more difficult to treat than epidermal.7
Pathogenesis
The skin pigment melanin is produced in melanocytes and stored in melanosomes, which are found in both melanocytes and keratinocytes.10 The enzyme tyrosinase is required for melanin synthesis.10 In dyschromia, there is dysregulation of intrinsic factors that regulate pigmentation, including signals from keratinocytes, endothelial cells, and fibroblasts as well as hormones from inflammatory cells and the nervous system.10 Exposure to ultraviolet (UV) radiation is a well-known extrinsic factor that increases skin pigmentation through upregulation of these intrinsic factors.10
