Diffuse hyperpigmentation of the skin: a clinicopathologic approach to diagnosis.

There are multiple causes of diffuse hyperpigmentation of the skin (DHP) and determination of the exact etiology can sometimes be difficult. A systematic classification based on both clinical and pathological findings that should aid the clinician who is confronted with this situation is presented in this article. The skin diseases that cause DHP are classified based on the pigment characteristics (melanin, non-melanin), pigment distribution (epidermal, epidermal-dermal, dermal) and density of melanocytes (normal, increased). The intent of this review is to provide a "histopathological tool" that increases diagnostic accuracy in the evaluation of a patient with DHP.