Skin

Question 1

2. What types of fibres are found in the layer underneath the epidermis?

Answer 1

Collagen

Elastic fibres

Question 2

3. What layers make up the epidermis?

Answer 2

Basal membrane – stem cells that differentiate into keratinocytes as they move up the epidermis
Stratum spinosum – spines (desmosomes) that connect keratinocytes
Stratum granulosum – cells die and lose nuclei- keratin shells remain and from water tight barrier
Stratum corneum

Question 3

5. How is palmar-plantar skin different from skin in other parts of the body?

Answer 3

There are no sebaceous glands

There is a very thick corneal layer

Question 4

6. Describe the effects of ageing on the skin.

Answer 4

Skin becomes fragile with very little epidermis

Collagen and elastic fibres are of poor quality

Question 5

7. List some different types of inflammatory reactions patterns in the skin.

Answer 5

Vesiculobullous – forms bullae 
Spongiotic – becomes oedematous 
Psoriasiform – becomes thickened
Lichenoid – forms a sheeny plaque 
(in the dermis)
Vasculitic – associated with vasculitis 
Granulomatous – associated with granulomas

Question 6

8. What is bullous pemphigoid? Describe the macroscopic appearance.

Answer 6

Occurs in elderly patients on their flexor surfaces
Characterised by the formation of tense bullae

Autoimmune disorder driven by IgG and C3 which attack the basement membrane
They recruit eosinophils which release elastase which further damages anchoring proteins (anchoring lower keratinocytes to the basement membrane)

Question 7

10. How can bullous pemphigoid be definitively diagnosed?

Answer 7

Immunofluorescence will show IgG and C3 along the dermo-epidermal junction

Question 8

11. Describe the macroscopic appearance of pemphigus vulgaris.

Answer 8

Blisters are flaccid meaning that they rupture easily exposing a red raw surface underneath. Blisters are intra epidermal then epidermis sloughs off

Question 9

12. Outline the pathophysiology of pemphigus vulgaris.

Answer 9

IgG-mediated disease where the damage is occurring within the keratinocyte layers

Question 10

13. What is acantholysis?

Answer 10

Loss of intercellular connections leading to loss of cohesion between keratinocytes

Question 11

14. Describe the macroscopic appearance of pemphigus foliaceus.

Answer 11

You rarely see intact bullae because they are so thin and fragile
You are likely to see some flaky remnants of old bullae

IgG-mediated attack on the outer layer of keratinocytes (where the stratum corneum is found)

Question 12

18. What is hyperparakeratosis?

Answer 12

Thickening of the skin on the surface where the patient has been scratching
The epidermis gets thicker

Question 13

20. What are the main immune mediators in eczema?

Answer 13

T-cell mediated
Eosinophils are also recruited
NOTE: this pattern is also seen in drug reactions

Question 14

1. How is the keratinocyte turnover time different in psoriasis compared to normal skin?

Answer 14

Normal skin turnover = 50 days (time for a keratinocyte to go from the bottom of the epidermis to the top)
Psoriasis = 7 days
This leads to thickening of the epidermis and you get a layer of parakeratosis at the top

Question 15

23. Which layer of the epidermis disappears in plaque psoriasis and why?

Answer 15

Stratum granulosum – there is not enough time to form it

Question 16

24. What can neutrophil recruitment to the epidermis in plaque psoriasis cause?

Answer 16

Formation of Munro’s microabscesses

Question 17

25. What is lichen planus and what are its main features?

Answer 17

Lichenoid reaction pattern
T-cell mediated
Presents with papules and plaques that are slightly purplish in colour on the wrists and arms
In the mouth it presents as white lines (Wickham striae)

Question 18

26. Describe the histological appearance of lichen planus.

Answer 18

Distinction between dermis and epidermis is difficult to see due to lymphocyte-mediated destruction of the bottom layer of keratinocytes
There is band-like lymphocytic infiltration just under the epidermis
NOTE: this is also seen in mycosis fungoides

Question 19

Give an example of a vasculitic skin reaction

Answer 19

pyoderma gangrenosum

Question 20

29. Which histological feature is classic of seborrhoeic keratosis?

Answer 20

Horn cysts – entrapped keratin surrounded by proliferating epidermis
NOTE: the epidermis is proliferating in an orderly manner

Question 21

30. Describe the appearance of a sebaceous/epidermal cyst.

Answer 21

Smooth surface 
Non-mobile 
Tend to have a punctum
Can get infected/rupture 
Can smell really bad

Question 22

32. Describe the macroscopic appearance of a basal cell carcinoma.

Answer 22

Rolled, pearly edge with a central ulcer and telangiectasia

Question 23

33. Describe the histological appearance of a basal cell carcinoma.

Answer 23

Cancer arises from the keratinocytes along the bottom of the epidermis (basal cells)
They can infiltrate through the basement membrane
They are locally infiltrative but don’t metastasise

Question 24

34. What is Bowen’s disease?

Answer 24

Squamous cell carcinoma in situ

Question 25

35. Describe the histological appearance of a benign junctional naevus.

Answer 25

Melanocytes expand in their normal position sitting on the basal layer and form nests
They are circumscribed and uniformly pigmented

Question 26

36. Describe the normal migration of melanocytes as they mature.

Answer 26

As they mature they become smaller and go deeper

Question 27

37. What are some clinical signs suggestive of a malignant melanoma?

Answer 27

Asymmetry 
Border irregularity 
Colours 
Diameter
Evolution

Question 28

38. Describe the histological appearance of malignant melanoma.

Answer 28

Melanocytes start migrating upwards through the epidermis (pagetoid spread)
They become active and lose the ability to differentiate
Melanoma thickness > 4 mm has a > 50% mortality