Lecture 28

What are the four main skin entry points?

Epidermal barrier, adnexal barrier, vessels and support structures

What is Hyperkeratosis?

A condition characterized by excess keratin formation leading to a thickened stratum corneum.

What clinical signs can indicate Hyperkeratosis?

Scaling, crusting, or greasiness of the skin.

Differentiate between Orthokeratotic and Parakeratotic keratinization.

Orthokeratotic shows complete cornification with anucleated cells; Parakeratotic shows partial cornification with nucleated cells.

What does Epidermal Hyperplasia (acanthosis) signify?

An increase in the number of cells in the epidermis, often in the stratum spinosum.

What is Epidermal Dysplasia and why is it significant?

Abnormal development of tissues that can progress to neoplasia, characterized by loss of keratinocyte organization.

What is the effect of Apoptosis in the epidermis?

It is a non-inflammatory response indicating programmed cell death.

What does Atrophy refer to in terms of skin response and what clinical sign would you associate with it?

A decrease in the number and size of skin cells due to sublethal injury. Would typically see thinned skin

What are the two types of Oedema observed in skin?

Ballooning degeneration (intracellular) and Spongiosis (intercellular).

What is the difference between the two types of oedema seen in skin

Ballooning degeneration is intracellular whereas spongiosis is intercellular and occurs between keratinocytes

Define Acantholysis.

Disruption of intercellular junctions between keratinocytes, common in immune-mediated disorders and bacterial infections

What causes Hyperpigmentation?

Increased numbers of melanocytes, increased melanin production, and endocrine dermatoses.

What are the potential causes of Hypopigmentation?

Decreased number of melanocytes, reduced melanin production, or copper deficiency.

What is Dermatitis?

Inflammation of the dermis characterized by erythema, swelling, and leukocyte migration.

What is Dermal Atrophy?

Decreased quantity of collagen fibers and fibroblasts leading to thin, translucent skin clinically.

What does Fibrosis refer to in skin response?

Formation of granulation tissues in response to skin injuries leading to scar formation.

What is proud flesh and what is it a result of

Proud flesh is a result of granulation tissue proliferation but extends beyond its boundary and creates raised, excessive scar tissue.

What is collagen dysplasia

A rare condition which is the inherited abnormality of collagen that results in decreased tensile strength and increased ability of the skin to stretch

What type of deposits result in thick, puffy skin

Mucin deposits

What causes calcinosis cutis

The deposition of calcium salts in the skin and subcutaneous tissue (dermis layer)

What is the significance of Chronic Dermatitis?

Caused by foreign bodies or autoimmune reactions, characterized by neutrophil, macrophage or eosinophil accumulations depending on the type of inflammation

What would you see in a perivascular inflammatory pattern

inflammatory cells are around the blood vessels

What would you see in a vascular inflammatory pattern

inflammatory cells are present in the endothelial wall

What would you see in an interface inflammatory pattern

inflammatory cells present at the interface of dermis and epidermis, which can either be cell poor or rich

What would you see in a nodular inflammatory pattern

inflammatory cells are present in nodular aggregations

Define Atrophy in the context of hair follicles.

A gradual reduction in size of hair follicles due to various pathological conditions.

What is Folliculitis?

Inflammation of the hair follicle affecting most domestic animals.

What is sebaceous adenitis

An inflammatory condition affecting the sebaceous glands

What is hidradenitis

Inflammation of the apocrine glands

What are Primary Lesions in skin pathology?

Direct results of underlying disease processes originating from normal skin.

What is Panniculitis and its typical causes:

Panniculitis is an inflammation of the fat layer beneath the skin, typically caused by infection, trauma, or immune-mediated conditions.

Define Macule

A circumscribed flat area of discoloration of the skin, up to 1 cm in diameter. Can be red or black colour or other colours

Define Patch

A macule over 1 cm in diameter

Define Papule

A solid elevation of the skin, up to 1 cm in diameter

Define Plaque

A large, flat-topped elevation formed by extension or coalescing of papules

Define Nodule

A circumscribed solid elevation extending to the deep layers, >1 cm diameter, also known as a neoplasm

Define Vesicle

A circumscribed, elevated, fluid-filled lesion, < 1cm in diameter

Define Bulla

A vesicle over 1 cm in diameter

Define Pustule

A circumscribed, small, pus filled elevation of the epidermis

Define Abscess

A well demarcated cavity resulting from pus accumulation in dermis and subcutis

Define Wheal

A firm, circumscribed raised elevation of the skin due to dermal oedema

Define Scale

An accumulation of loose fragments of cornified skin, primary occurs in icthyosis, secondary can be seen in condiions such as fungal dermatitis

Define Crust

Dried exudate composed of cell debris, scale, fluid blood on the skin surface, can occur in photosensitisation or staphylococcal infection etc

Define Comedo

Distended hair follicle with plug of stratum corneum and sebum, clinically these look like pimples

Define Hypertrichosis

More hair than normal

Define Hypotrichosis

Less hair than normal

Define Epidermal collarette

A circular rim of keratin scale after loss of the roof of vesicle or pustule

Define Erosion

Epidermal defect that spares the basement membrane

Define Ulcer

Loss of epidermis, basement membrane, and at least the superficial portion of dermis

Define Lichenification

Thickening and hardening of the skin

Define Callus

A thickened, rough, alopecic, often lichenified plaque that develops on the skin usually at pressure points