Pathology of Rashes

Question 1

What are the functions of the skin?

Answer 1

Strong barrier to antigens and organisms, thermoregulation, fluid and electrolyte balance, endocrine function, protection from UV rays, immune function, sensory function

Question 2

What makes up the epidermis in normal skin?

Answer 2

Mainly maturing squamous cells

Question 3

Where is the mitotic pool of the skin?

Answer 3

Basal layer

Question 4

Where are melanocytes found?

Answer 4

At the Dermo-epidermal junction

Question 5

What is the ration of melanocytes to basal cells?

Answer 5

1:10

Question 6

What cell type makes up the epidermis?

Answer 6

Stratified keratinising squamous cells

Question 7

What is found in the prickle layer?

Answer 7

Prominent desmosomes

Question 8

What is the granular layer rich in?

Answer 8

Keratohyalin granules

Question 9

What cells make up the corneal layer?

Answer 9

Differentiated keratinised cells

Question 10

What is house dust?

Answer 10

Corneocytes shed from the skin surface

Question 11

What do melanocytes do and where are they found?

Answer 11

Synthesise melanin and transfer pigment to keratinocytes via dendritic processes; found in basal layer

Question 12

What is the function of Langerhans cells and where are they found?

Answer 12

Dendritic cells that act as sentinels monitoring the environment for antigens, important in initiating inflammation; located in upper and mid-epidermis

Question 13

What makes up the matrix of the dermis?

Answer 13

Type I and type III collagen

Question 14

What are some structures that can be found in the dermis?

Answer 14

Elastic fibres and ground substances (hyaluronic acid and chondroitin sulphate)

Question 15

What is the papillary dermis like and where is it found?

Answer 15

Thin; lies just beneath the epidermis

Question 16

What are some features of the reticular dermis?

Answer 16

Thicker bundles of type I collagen, contains appendages (e.g sweat glands, pilosebaceous units)

Question 17

What makes up the basement membrane of the epidermis?

Answer 17

Laminin and collagen IV

Question 18

What does Hyperkeratosis mean?

Answer 18

Increased thickness of keratin layer

Question 19

What does Parakeratosis mean?

Answer 19

Persistence of nuclei in the keratin layer

Question 20

What does Acanthosis mean?

Answer 20

Increased thickness of the epithelium

Question 21

What is the definition of Papillomatosis?

Answer 21

Irregular epithelial thickening

Question 22

What is Spongiosis?

Answer 22

Oedema fluid between squames which causes an increase in the prominence of intercellular prickles

Question 23

What happens if Spongiosis is severe?

Answer 23

Vesicles become filled by oedema fluid

Question 24

What are the classes of inflammatory skin diseases?

Answer 24

Spongiotic-intraepidermal oedema (e.g eczema), Psoriasiform-elongation of the rete ridges (e.g psoriasis), Lichenoid-basal layer damage (e.g lichen planus), Vesiculobullous-blistering (e.g pemphigoid)

Question 25

What genes are associated with psoriasis?

Answer 25

Specific special HLA types

Question 26

What is the Koebner phenomenon?

Answer 26

New lesions of psoriasis arise at sites of trauma

Question 27

How it epidermal hyperplasia linked to psoriasis?

Answer 27

It increases epidermal turnover

Question 28

How is the complement system linked to psoriasis?

Answer 28

Proposed pathogenesis mechanism-complement mediated attack on keratin layer, complement attracts neutrophils to keratin layers causing Munro micro-abscesses

Question 29

What characterises Lichenoid disorders?

Answer 29

Damage to the basal epidermis

Question 30

What is the prototypic condition of Lichenoid disorders?

Answer 30

Lichen planus

Question 31

What is the common appearance of Lichenoid disorders?

Answer 31

Itchy flat-topped violaceous papules

Question 32

What is the histology of Lichen planus?

Answer 32

Irregular sawtooth acanthosis, hypergranulosis and orthohyperkeratosis, band-like upper dermal infiltrate of lymphocytes, basal damage with formation of cytoid bodies

Question 33

What other Lichenoid disorders resemble lichen planus?

Answer 33

Discoid lupus, some drug rashes

Question 34

What are two life threatening Lichenoid disorders, and how do they differ from lichen planus?

Answer 34

Erythema multiforme and Toxic epidermal necrolysis; have more marked vacuolar interface change than lichen planus

Question 35

What are the primary feature of Immunobullous disorders?

Answer 35

Blisters

Question 36

What can sometimes occur as a secondary phenomenon in many skin diseases (e.g eczema, herpes, burns)?

Answer 36

Vesicles and bullae

Question 37

What are some examples of Immunobullous disorders?

Answer 37

Pemphigus, Bullous pemphigoid, Dermatitis herpetiformis

Question 38

What is Pemphigus?

Answer 38

Rare autoimmune bullous disease, loss of integrity of epidermal cell adhesion

Question 39

Who normally gets Pemphigus?

Answer 39

Has equal sex incidence, usually middle-aged people

Question 40

What is a feature of all forms of Pemphigus?

Answer 40

Acantholysis

Question 41

Can Pemphigus be fatal?

Answer 41

Yes-has variable severity and responds to steroids

Question 42

How many subtypes of Pemphigus are there?

Answer 42

4-all separable clinically and histologically

Question 43

What type of Pemphigus is responsible for 80% of cases?

Answer 43

Pemphigus vulgaris

Question 44

What happens in Pemphigus vulgaris?

Answer 44

IgG auto-antibodies are made against desmoglein 3, immune complexes form on cell surface causing compliment activation and protease release disrupting the desmosomes, end result is acantholysis

Question 45

What does desmoglein 3 do in the skin?

Answer 45

Maintains desmosomal attachments

Question 46

What is acantholysis?

Answer 46

Lysis of intercellular adhesion sites

Question 47

What areas are involved in Pemphigus vulgaris?

Answer 47

Scalp, face, axillae, groin and trunk

Question 48

Can the mucosa become affected in Pemphigus vulgaris?

Answer 48

Yes- extensive mucosal involvement may be fatal

Question 49

What does Pemphigus vulgaris produce on the skin?

Answer 49

Produces fluid filled blisters which rupture to form shallow erosions

Question 50

How does Bullous pemphigoid differ from Pemphigus vulgaris?

Answer 50

There is no evidence of acantholysis (only formation of sub-epidermal blisters)

Question 51

What occurs in Bullous pemphigoid?

Answer 51

Circulating IgG react with major and/or minor antigen of the hemidesmosomes anchoring basal cells to the basement membrane, causing local complement activation and tissue damage

Question 52

What does immunofluorescence of Pemphigus vulgaris show?

Answer 52

Linear IgG+ complement deposited around the basement membrane

Question 53

What do old lesions of Pemphigus show?

Answer 53

Re-epithelialisation of their floor, mimicking Pemphigus vulgaris

Question 54

What is Dermatitis herpetiformis?

Answer 54

Relatively rare autoimmune bullous disease, intensely itchy symmetrical lesions

Question 55

What is Dermatitis herpetiformis associated with?

Answer 55

Coeliac disease, HLA-DQ2 haplotype

Question 56

Where do lesions tend to appear in Dermatitis herpetiformis?

Answer 56

Elbows, knees and buttocks (often excoriated)

Question 57

What is the hallmark of Dermatitis herpetiformis?

Answer 57

Papillary dermal micro-abscesses

Question 58

What do 90% of people with Dermatitis herpetiformis also have?

Answer 58

Gluten sensitive enteropathy (may be asymptomatic)

Question 59

What does DIF show in Dermatitis herpetiformis?

Answer 59

IgA in dermal papillae

Question 60

What occurs in Dermatitis herpetiformis?

Answer 60

IgA antibodies target gliadin components of gluten but cross react with connective tissue matrix proteins, immune complexes form in dermal papillae and activate complement and generate neutrophil chemotaxis

Question 61

What does the distribution of acne reflect?

Answer 61

Sebaceous gland sites (face, upper back, anterior chest)

Question 62

What is the suspected aetiology of acne?

Answer 62

Increased androgens at puberty, possible increased androgen sensitivity of sebaceous glands, keratin plugging of pilosebaceous units, infection with anaerobic bacterium bacterium Corynebacterium acnes

Question 63

How does acne develop?

Answer 63

Sebum produced by sebaceous glands plugs pilosebaceous unit, keratin and sebum build up produce comedones, rupture causes acute inflammation plus foreign body granulomas

Question 64

What are comedones?

Answer 64

Black/whitehead spots

Question 65

What gender is Rosacea more common in?

Answer 65

Females

Question 66

What occurs in Rosacea?

Answer 66

Recurrent facial flushing, visible blood vessels, pustules, thickening of skin (rhinophyma)

Question 67

What are some triggers of Rosacea?

Answer 67

Sunlight, alcohol, spicy foods, stress, some respond to tetracyclines

Question 68

What is the pathology of Rosacea?

Answer 68

Vascular ectasia, patchy inflammation with plasma cells, pustules, perifollicular granulomas, follicular demodex mites often noted