HYPERCHROMIA (HYPOCHROMIA)

HYPERCHROMIA, HYPOCHROMIA (hypo-, hypopigmentation), intensification or weakening of skin coloring, depending on the more significant deposition of pigment or its loss in certain areas of the skin. Hyperchromia arises as a result of 1) increase of the pigment normally existing in the skin; 2) penetration into the skin of coloring matter from the blood, which undergoes a series of transformations here; 3) deposition in the skin of coloring substances foreign to the body (argyria, arsenical pigmentations, etc.). Primary and secondary hyperchromias are distinguished. Primary may be caused by congenital predisposition (e.g. naevus pigmentosus), external chemical, thermal, light and other influences, internal causes (e.g. Addison's disease, hemochromatosis, etc.) and unknown causes (e.g. melasma idiopathicum). Secondary hyperchromia occurs after many skin rashes, especially itchy ones (pediculosis, disease of tramps, psoriasis eruptions, etc.). Hyperchromia may be temporary when its cause is removable, or it may be permanent. Hypochromia also arises primarily (for example in vitiligo) or develops secondarily in the place of a former eruption, for example psoriasis, Wilson's lichen, syphilid, etc. An interesting example of hypochromic disks is the so-called solar leukoderma: pigmentation from tanning occurs only on healthy skin and is absent on areas where there is peeling, which makes the latter appear white against the general bronze background.