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SECONDARY LESIONS - Lesions that evolve from primary lesions or are created by patient or external factors, i.e. trauma, medications.
SECONDARY SKIN LESIONS

SCALE - EPIDERMAL COLLARETTE CRUST SCAR ULCER- EROSION EXCORIATION LICHENIFICATION HYPO- or HYPERPIGMENTATION COMEDO HYPERKERATOSIS FISSURE

SCALE - An accumulation of loose fragments of the horny layer of the skin (cornified cells).

EPIDERMAL COLLARETTE - A special type of scale arranged in a circular rim of loose keratin flakes. It represents the remnants of what once formed the root of a vesicle, bulla or pustule.

This slide demonstrates scales in a hypothyroid dog.
This slide demonstrates papules and epidermal collaretes in a dog with superficial pyoderma.
CRUST - Dried exudate on the surface of a lesion.
This slide demonstrates crusts and ulcers in the ear of a cat with systemic lupus erythematosus.
SCAR - An area of fibrous tissue that has replaced the damaged dermis or subcutaneous tissue.
This slide demonstrates scars on the body of a dog that was burned in a house fire.
ULCER - A break in the continuity of the epidermis with exposure of the underlying dermis.

EROSION - A shallow ulcer that does not penetrate into the dermis.

This slide demonstrates ulcers on the ventral abdomen of a dog with cutaneous lymphosarcoma.
This slide demonstrates very superficial erosions, crusts, and epidermal collarettes on the body of a dog with pemphigus follaceus.
EXCORIATION - a superficial removal of the epidermis caused by scratching, biting or rubbing. Most excoriations are self-produced and caused by pruitus.
This slide demonstrates excoriations on the head and ear of a dog with scabies.
HYPOPIGMENTATION - Loss of epidermal melanin. Lack of pigment in the hair is call leukotrichia.

HYPERPIGMENTATION - Increased epidermal and occasionally dermal melanin. Excess pigment in the hair is called melanotrichia.

This slide demonstrates a hypopigmented nose. This dog had vitiligo.
LICHENIFICATION - A thickening and hardening of the skin characterized by exaggeration of the superficial skin markings.

HYPERKERATOSIS - An increase in thickness of the horny layer of the skin.

This slide demonstrates hyperkeratotic footpads in a dog with pemphigus foliaceus.
COMEDO - (blackhead) A dilated hair follicle filled with cornified cells, sebaceous material, and microorganisms.
This slide demonstrates comedones on the ventral abdomen of a cushingoid dog.
FISSURE - A crack or cleft into the epidermis, or through the epidermis into the dermis caused by disease or injury.

ALOPECIA - Loss of hair. May be primary (i.e. endocrine alopecia) or secondary to inflammation of the hair follicle.

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