the dermatological response to damage

Question 1

list potential causes of damage to the skin

Answer 1

• microbial (bacteria, fungi, virus, protozoa, rickettsia)
• ectoparastitic
• traumatic
• chemical
• auto-immune
• allergic
• endocrine/metabolic
• nutritional
• environmental

lots of causes but limited bumber of ways the skin can respons

Question 2

list ways the epidermis responds to damage

Answer 2

• hyperkeratosis
• acanthosis
• vesicle/pustule formation
• hyperpigmentation/hypopigmentation
• crusting

Question 3

list ways the dermis responds to damage

Answer 3

• erythema
• oedema
• thickening

Question 4

what is hyperkeratosis and how does it manifest

Answer 4

increased depth of the cornified layer (due to body trying to protect self
causes increased scale (as corneocytes slough) and crusts

Question 5

what is scale

Answer 5

production of abnormal or excessive scale (exfoliated corneocytes)
- indicates abnormality of keratinisation
- causes surface flakes oof scale on skin surface/in coat (dandruff)

Question 6

what is a comedone

Answer 6

• type of follicular hyperkeratinosis
• keratinaceous plugs in hair follicle infundibula
• “blackhead”
• particular feature of demodicosis or endocrinopathies

Question 7

what is the difference between primary and secondary hyperkeratinosis

Answer 7

• primary is rare in animals (ex. icthyosis in goldens)
  secondary defects are common
• non-specific but indicative of increased turnover of epidermis or imbalance between turnober and desquamation
• feature of lots of different skin diseases (metabolic, infectious, parasitic, immune mediated, neoplastic)

Question 8

what is acanthosis

Answer 8

increased depth of the epidermis (all layers, not just stratum corneum as in hyperkeratinosis)

basically a callus

Question 9

what causes acanthosis

Answer 9

1. repeated low grade blunt trauma
2. release of cytokines
3. increased division of basal epidermal cells
4. increased depth of epidermis

Question 10

what is lichenification

Answer 10

lesion resulting from thickening and hardening of the epidermis and characterised by exaggeration of the superficial skin markings
- a non-specific finding of many diseases with chronic inflammation or friction
- may involve hyperkeratinosis and acanthosis
- indicative of a long term skin disease, does NOT appear overnight
- often goes together with hyperpigmentation

Question 11

what is the difference between a vesicle and a pustule

Answer 11

vesicle: filled with clear sterile fluid (a blister)
pustule: filled with pus

Question 12

what is a vesicle

Answer 12

• short lived in domesticated animals as epidermis is very fragile (therefore rarely seen) but you will see subsequent erosions and ulcers
• usually occurs with viruses or autoimmune diseases
  *erosion: superficial; basal layer of epidermis not breached
  *ulcer: dermis is exposed

Question 13

what is a pustule

Answer 13

• small circumscribed elevation of the epidermis that is filled with pus
• usually associated with infection
• in autoimmune diseases, contents can be sterile

Question 14

what is hyperpigmentation and what causes

Answer 14

abnormal pigment to the skin.
- non-specific
- commonly post-inflammatory
- some endocrine disorders cause
- melanocytes important for pigmentation of skin disturbed (play a role in local modulation of cutaneous inflammation)

Question 15

what is hypopigmentation and when is it commonly seen

Answer 15

• abnormally less pigment to the skin
• feature of diseases affecting the basal epidermis and dermo-epidermal junction
• autoimmune diseases and neoplsia (epitheliotropic lymphoma)
• also occurs post-inflammatory (how freezebranding works)

Question 16

what are crusts/how are they formed

Answer 16

• scabs
• formed when dried exudate, serum, pus, blood, cells, scales or medications adhere to skin surface
• variable in cellularity and colour
• may contain organisms
• always secondary
• caused by many exudative and ulcerative diseases

Question 17

what is erythema and how does it appear

Answer 17

redness of the skin
1. damage
2. release of pro-inflammatory mediators
3. vasodilation of dermal vessels
4. erythema

common in infectious and allergic processes

Question 18

how does eodema work

Answer 18

1. mediated by histamine and other cytokines
2. increased vascular permeability
3. leakage of tissue fluid

Question 19

what is an urticarial lesion

Answer 19

raised oedematous areas that pit on pressure

Question 20

what is dermal thickening associated with

Answer 20

• longer standing allergic reactions (cellular infiltrate)
• chronic inflammatory conditions (increased connective tissue components)

Question 21

what is alopecia and what causes it

Answer 21

hair loss
- can be complete or partial
- due to failure of hair to grow properly (endocrinopathies and hair follicle dysplasia) or damage to hair follicle/shaft (trauma, infection, parasites, neoplasia, immune/autoimmune disease, nutritional deficiency)