Hyperpigmentation may be localized, as in the case of post-inflammatory hyperpigmentation or melasma, or more diffuse in its presentation. Diffuse hyperpigmentation tends to be associated with metabolic causes, certain medications, malignancy, or autoimmune or infectious etiologies. Since diffuse hyperpigmentation may be associated with malignancy or may be improved through treatment of the underlying disease process or insufficiency or elimination of the causative medication, it is important to identify the cause.
Although not as common, many cases of malignancy, especially related to melanoma, have been known to cause diffuse hyperpigmentation. This is more common in patients with metastatic disease and/or those patients who unfortunately present with melanoma of an unknown primary origin.