Equine Pathology Workbook

Skin Lesions

Vitiligo or Leukoderma

The term vitiligo or leukoderma is used to describe areas of in the skin and hair. The area of depigmentation often has a hyperpigmented border. Depigmentation occurs due to the absence or destruction of in the skin. Vitiligo often occurs at the site of a healed injury.

Macule

A macule is a flat area of pigmentation less than one centimetre in diameter. Macules are not palpable, but can be identified through visual examination. . Macules can be an increase, decrease or change in pigmentation.

Patch

A patch is a flat area of abnormal pigmentation that is diameter. In effect, a patch is an oversized macule.

than one centimetre in

Papule

A papule is a circumscribed, solid, lesion less than one centimetre in diameter. Papules have a firm consistency, and there is no fluid or semi-fluid fill. Papules are usually caused by an infiltrate into the epidermal papillae.

Plaque

A plaque is a circumscribed, solid, elevated lesion greater than one centimetre in diameter. A plaque is an oversized papule. In some cases, plaques are formed by a confluence of papules.

Nodule

A nodule is described as a firm, circumscribed lesion that extends into the . Generally, nodules are more than one centimetre in diameter. Nodules are usually caused by dermal infiltrate or subcutaneous fat into the dermis.

Tumor

A tumor is a firm, circumscribed lesion that extends into the dermis and is larger than a nodule.

Papilloma

projections protrude above the skins surface. It is caused by upward

extension of the dermal papillae. Usually covered by hyperplastic epidermis.

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