Skin Pathology

Question 1

Define hyperkeratosis

Answer 1

Increased thickness of keratin layer

Question 2

Define parakeratosis

Answer 2

Persistence of nuclei in the keratin layer

Question 3

Define Acanthosis

Answer 3

Increased thickness of epithelium/ epidermis

Question 4

Define papillomatosis

Answer 4

Irregular epithelial thickening

Question 5

Define spongiosis

Answer 5

Oedema fluid between squamous cells in epidermis
Increases prominence of intercellular prickles (desmosomes)
In severe cases - vesicles filled by oedema fluid develop.

Question 6

What are the 4 classifications of inflammatory skin diseases

Answer 6

•Spongiotic-intraepidermal oedema e.g. eczema

•Psoriasiform-elongation of rete ridges e.g. psoriasis

•Lichenoid-basal layer damage e.g. lichen planus and lupus

•Vesiculobullous-blistering e.g. pemphigoid, pemphigus and dermatitis herpetiformis

Question 7

What are the 3 main types of eczema

Answer 7

atopic, irritant contact and allergic contact

Question 8

What are the 3 stages of eczema

Answer 8

•Acute – massive spongiosis and vesiculation
•Subacute-less spongiosis – more acanthosis and scale
•Chronic-minimal spongisosis – prominent acanthosis and scale

Question 9

Allergic contact eczema Pathophysiology

Answer 9

• Langerhans cells present antigen to T-lymphocytes
• Sensitised Memory T-cells in nodes recognise antigen
• T-lymphocytes then sent to epidermis
• Infiltrate epidermis and cause spongiotic eczematous reaction

Eosinophils often present (also a feature of drug trigger)

Question 10

Psoriasis pathophysiology

Question 11

Psoriasis diagnostic clues on microscopy

Question 12

What are lichenoid disorders? Name some examples

Answer 12

Conditions characterised by damage to basal epidermis. Common condition is lichen planus
Other conditions include - discoid lupus, certain drug rashes, erythema multiform, toxic epidermal necrolysis

Question 13

Lichen planus appearance

Answer 13

Itchy flat topped violaceous papules on skin & sore in the mouth

Question 14

Lichen planus histology

Answer 14

•Irregular sawtooth acanthosis

•Hypergranulosis and orthohyperkeratosis

•Band-like upper dermal infiltrate of lymphocytes

•Basal damage with formation of cytoid bodies

Question 15

What immunobullous disorders

Question 16

name 3 examples of immunobullous diseases

Answer 16

Pemphigus (Pemphigus vulgaris)
Bullous pemphigoid
Dermatitis herpetiforms

Question 17

What is Pemphigus

Answer 17

Rare autoimmune bullous disease that causes acantholysis & loss of integrity of epidermal cell adhesions.

Question 18

Pemphigus vulgaris pathophysiology

Answer 18

•IgG auto-antibodies made against desmoglein 3
•Desmoglein 3 maintains desmosomal attachments
•Immune complexes form on cell surface
•Complement activation and protease release
•Disruption of desmosomes
•End result is ACANTHOLYSIS

Question 19

What is acantholysis

Answer 19

lysis of intercellular adhesion sites

Question 20

Pemphigus vulgaris presentation

Answer 20

Fluid filled blisters that rupture to form shallow erosions
Involves skin - especially scalp, face, axillae, groin & trunk
Involves mucosa - especially mouth & respiratory tract

Question 21

Pemphigus vulgaris vs Bullous pemphigoid

Answer 21

Pemphigus vulgaris
- antibodies against epidermal cell desmosomes adhesions
- causes ancatholysis
- presents with shallow erosions

Bullous pemphigoid
- antibodies against hemidesmosomes
- causes loss of anchoring between basal cells & basement membrane
- presents with subepidermal blisters/ bullae

Question 22

Bullous pemphigoid pathophysiology

Answer 22

Circulating antibodies (IgG) react with a major and/or minor antigen of the hemidesmosomes anchoring basal cells to basement membrane. The result is local complement activation and tissue damage

Basal cells/ epidermis lifts off of basement membrane forming a bulla (filled with fluid & some inflammatory cells)