1.1 Macule

Macule, patch.

A flat, non-palpable, localized change in color of skin. Usually sharp borders.

If larger than 1 cm: patch.

Colors: red, brown, black, white, blue, yellow.

Size: several millimeters. 

Petechia (punctate bleeding into skin), purpura (small areas of bleeding), hematoma (larger areas of bleeding), deposition of pigmented material of different origin.

Can appear anywhere on skin; for example macula exanthema.

On mucosa: enanthem.

May develop into hive or a papule.

May over time develop additional scaling.

 
Often associated with papules, vesicles and pustules.

Large red patch = erythema.

Erythroderma (generalized redness, often infiltrated).

Flush (acute transient facial erythema).

Drug induced eruption, macular lentigo, viral exanthema, vitiligo, pytiriasis versicolor.

Vascular dilation, either because of aberrant vessels or inflammatory mediators (red): endogenous or exogenous pigment, for example melanin (brown-black, blue-gray), hemoglobulin (red-blue), hemosiderin (brown) lipids (yellow), loss of pigment (white) , external deposition of foreign body material (trauma, tattoo).