Macule A
circumscribed flat area of change in colour of the skin less
than 1 cm in diameter.
Patch
Same as macule but exceeding 1 cm in diameter.
The change in colour may result from pigment
loss or excess, erythema, or haemorrhage. Erythematous
macules are common in inflammatory diseases of the superficial
dermis, such as allergies.
Petechiae are pin-point macules caused
by haemorrhage of less than 1 cm in diameter. Ecchymoses
are patches caused by haemorrhage of more than 1 cm in diameter.
Cutaneous haemorrhages may reflect thrombocytopenia,
defects in coagulation, or vasculitis.
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Macular areas of hyperpigmentation in a dachshund with acanthosis
nigricans
A
circumscribed flat area of change in colour of the skin less
than 1 cm in diameter.