Skin pathology

Question 1

Nikolsky’s sign

Answer 1

Do blisters rupture when rubbed?
Positive - superficial
Negative - deep

Question 2

Nikolsky positive
Superficial flaccid blisters
Type II hypersensitivity - IgG against desmoglein 3
Tombstoning (acantholysis)
IgG and C3 between keratinocytes (intra-epidermal)
Fluid fills space between cells

Answer 2

Pemphigus vulgaris

Question 3

Nikolsky negative
Deep tense blisters
Type II hypersensitivity - IgG against collagen XVII of hemidesmosomes
IgG and C3 between keratinocytes + BM (sup-epidermal)
Fluid + eosinophils fill space

Answer 3

Pemphigoid

Question 4

House analogy - pemphigus vs. pemphigoid

Answer 4

Pemphigus = gaps between first layer of bricks, but bricks stay attached to ground
Pemphigoid = house lifted from ground

Question 5

Type II hypersensitivity - IgG against desmoglein 1
Very superficial
IgG and C3 sub-corneal
Slowly extending rash on face, scalp, upper back
Tzanck smear

Answer 5

Pemphigus foliaceus

Question 6

Most superficial - bullous pemphigoid, pemphigus vulgaris, pemphigus foliaceus

Answer 6

Pemphigus foliaceus
Pemphigus vulgaris
Bullous pemphigoid

Question 7

Skin anatomy

Answer 7

Epidermis (keratinocytes arranged into corneum, granulosum, spinosum, basale - sitting on BM - keratinocytes replicate + move upwards to replace)
Dermis (sweat glands, hair follicles, blood vessels, lymphatics; type I collagen)
Subcutaneous tissue (mostly fat)

Question 8

Thin epidermis

Answer 8

Elderly

Question 9

Thick stratum corneum
Stratum lucidum
Lack of glands / hair folliles

Answer 9

Palms + soles

Question 10

Acantholysis
Tzanck positive
Tombstoning

Answer 10

Due to separation between keratinocytes

Occurs in pemphigus (folaceus + vulgaris)

Question 11

Target shaped rash
Following infection (mycoplasma, HSV), penicillin allergy

Answer 11

Erythema multiforme

Question 12

Target shaped lesions + mucosal involvement

Answer 12

SJS

Question 13

Salmon pink scaly rash
Silvery scales
Munro abscesses (WBCs in corneum)
Auspitz sign (pinpoint bleeding)
Onchyolysis

Answer 13

Psorisasis

Question 14

Herald patch (single salmon pink scaly macule)
7d later pink rash in fir tree distribution

Answer 14

Pityriasis rosea

Question 15

Brown warty lesion on nose
Solar elastosis on biopsy
Progression to SCC?

Answer 15

Acitinic keratosis

Question 16

7Ps (polygonal, planar, papular, plaques, pearl sheen, pruritic)
Lymphocytic infiltration = saw tooth pattern
Epidermal-dermal inflammation

Answer 16

Lichen planus

Question 17

Rodent ulcer
Pearly telangiectasia
Very invasive

Answer 17

Basal cell carcinoma

Question 18

Itchy blisters on buttocks and elbows

Coeliac disease

Answer 18

Dermatitis herpetiformis

Question 19

Epidermal (keratinocyte) tumours

Answer 19

Benign - Solar (acitinic) keratosis, Bowen’s disease (SCC in situ)
Malignant - BCC, SCC

Question 20

Solar (acitinic) keratosis vs. Bowen’s

Answer 20

Basal layer vs. full thickness of epidermis

Question 21

Ulcerated nodule
Rolled border
Granulating base
Sun damage

Answer 21

SCC

Question 22

Breslow thickness

Answer 22

Melanoma

Question 23

IBD

Deep necrotic ulcers on legs

Answer 23

Pyoderma gangrenosum

Question 24

IBD

Tender, erythematous + warm nodules on legs

Answer 24

Erythema nodosum

Question 25

Pox virus
Pearly dome shaped lesions with central umbilicus
Very contagious

Answer 25

Molluscum contagiosum

Question 26

Macular, papular then vesicular

Answer 26

Chickenpox

Question 27

Fungal infection

Fine scaly lesion that then becomes pale in colour

Answer 27

Pityriasis versicolor

Question 28

Stuck on appearance

Answer 28

Seborrhoeic warts

Question 29

Palpable purpura
Arthritis
Abdominal pain
Nephritic syndrome
(IgA)

Answer 29

HSP