PIH within the dermis results from inflammationinduced
damage to basal keratinocytes, which release large
amounts of melanin. The free pigment is then phagocytosed
by macrophages, now called melanophages, in the upper
dermis and produces a blue-gray appearance to the skin at
the site of injury.13,14
CLINICAL MANIFESTATIONS
PIH typically manifests as macules or patches in the
same distribution as the initial inflammatory process. The
location of the excess pigment within the layers of the skin
will determine its coloration. Epidermal hypermelanosis
will appear tan, brown, or dark brown and may take
months to years to resolve without treatment.1
Hyperpigmentation within the dermis has a blue-gray
appearance and may either be permanent or resolve over
a protracted period of time if left untreated.1,15 The
intensity of PIH may also correlate with higher skin
phototypes (Figures 4A and 4B), although studies are
needed to confirm this finding. In addition, PIH can
worsen with ultraviolet (UV) irradiation or with persistent
or recurrent inflammation.16