PATHOLOGY- Inflammatory skin diseases Flashcards
What is the epidermis mainly composed of?
Epithelial cells
Melanocytes
What do epithelial cells do
They make keratin to make keratocytes
List the board categories non infectious inflammatory diseases can fall under
- Dermatitis/ psoriasis
- Blistering
- Connective tissue damage
- Skin lesions as a sign of systemic disease
- Skin lesions caused by metabolic disorders
Name the most common disease of the skin
Eczema/ dermatitis
What does eczema describe
A reaction pattern rather than a specific disease
How common is eczema in children
5% of children in the UK have eczema
What is another name for eczema?
Dermatitis
Name the stages of dermatitis
- Acute dermatitis
- Subacute dermatitis
- Chronic dermatitis
Describe the acute stage of dermatitis
Red skin
Weeping serous exudate
There may be some small vesicles
Describe the subacute phase of dermatitis
Skin is red and crusty
Less exudate
Very very itchy skin
Describe the chronic stage of dermatitis
Skin is thick and leathery
How does eczema look under a microscope during the acute phase?
You’ll see oedemas within the epidermis and fluid filled blisters (spongiosis)
How does eczema look under a microscope during the chronic stage
Epidermis has become thickened and and the normal undulations of the epidermis became quite pronounced
spongiosis is much less
Keratin layer is bigger and thicker
What is spongiosis
Intercellular oedema within the epidermis
Name the different types of of eczema
- Atopic eczema
- Contact irritant dermatitis
- Contact allergic dermatitis
- Dermatitis of unknown aetiology
Who usually has atopic eczema
Children with family history
Often associated with asthma and hay fever
What type of inflammatory disease is atopic eczema
A type 1 hypersensitivity reaction to an allergen
What is contact irritant dermatitis caused by
Direct injury to skin by irritant eg acid, alkali, strong detergent
What is contact allergic dermatitis caused by
Nickel, dyes, rubber
These act as happens which combine with epidermal protein to become immunogenic
What type of inflammatory disease is contact allergic dermatitis?
A delayed type 4 hypersensitivity reaction
What are dermatitis with an unknown aetiology categorised by?
Their morphological subtypes
List the 2 morphological subtypes dermatitis of unknown aetiology can fall under
- Seborrhoeic dermatitis
- Nummular dermatitis
Describe seborrhoeic dermatitis
Dermatitis that affects areas rich in sebaceous glands
EG scalp, forehead, upper chest
Describe nummular dermatitis
Coin shaped lesions
How common is psoriasis
Affects 1-2% of population
Describe how psoriasis looks
- Well defined, red oval plaques on extensor surfaces (knees, elbows, sacrum)
- Fine silvery scale
What happens if you pick at a scale caused by psoriasis (what is this called)
Removal of scale causes small bleeding portitis
This is called Auspitz sign
List some associating symptoms that people may psoriasis may present with
- Pitting nails
- Sero negative arthritis
Describe the appearance of psoriasis under a microscope
- Regular e longed club shaped rete ridges
- Thickening of epidermis over dermal papillae
- Parakeratotic (contains nuclei) scaled
- Collections of neutrophils in scale
What does parakeratoic mean
Contains nuclei
What is the appearance of psoriasis under a microscope called?
Psoriasiform hyperplasia
What do the clinical and microscopic features of psoriasis suggest?
They reflect massive cell turnover
Describe the pathogenesis of psoriasis
Trigger factor leading to a dysfunctional immune reaction
Talk through the aetiology of psoriasis
- Genetic factors
- Environmental trigger factors such as infection, stress, trauma and drugs
Which gene may be responsible for genetic psoriasis
Theres multiple loci on the psoriasis susceptibility or PSORS genes
Many of these loci lie in the region of major histocompatibility complex on chromosome 6p2
Name some diseases that are associated with psoriasis
- Arthropathy (5-10% associated)
- Psychosocial effects
- Cardiovascular disease
- Cancer increased risk of non melanoma skin cancer
What is the most common treatment plan for psoriasis and what problems can this cease?
UV light is the main treatment option
This is a risk factor for developing skin cancer
How can psoriasis manifest in the oral cavity?
- Geographical tongue
- Angry red patches on the hard palette
What is lupus erythematosus
It is an auto immune disorder primarily affecting connective tissues of the body
Which organ is mainly affected by lupus erythematosus
Can affect any part of the body but most importantly kidneys
What happens in lupus erythematosus
Autoantibodies are directed at various tissues
Which parts of the body are affected by systemic lupus erythematosus
Can affect all parts of the body eg:
- Brain
- Skin
- Renal system
- Can cause fever
Name the types of lupus erythematosus that affect the skin
- Discoid lupus erythematosus
- Systemic lupus erythematosus
Describe the clinical presentation of discoid lupus erythematosus
Affects only the skin
Leads to red scaly patches on sun exposed skin, can cause scarring
what does scalp involvement in discoid lupus erythematosus cause
Alpoecia
Describe the clinical presentation of systemic lupus erythematosus
It is a visceral disease that MAY involve the skin
Butterfly rashes on cheeks and nose
Describe how lupus erythematosus looks under a microscope
Thin atrophic epidermis, inflammation and destruction of adnexal structures
IgG deposited in basement membrane
How do we confirm a diagnosis of lupus erythematosus
- We create an antibody to the endogenous lupus antibodies
- Attach a fluorescent signal to the antibody
- Mix a sample of skin and the antibody
- if under a microscope you seen fluorescence then you have lupus erythematosus antigens in the sample
Name a condition that can give an almost identical histological presentation to lupus erythematosus
Dermatomyositis
What is Dermatomyositis
Peri ocular oedema and erythema (heliotropic rash)
What can Dermatomyositis cause
- Erythema in photosensitive distribution
- Myositis: proximal muscle weakness
What is Dermatomyositis associated with in adults
In adults 25% of Dermatomyositis cases are associated with underlying visceral cancer
What is Dermatomyositis characterised by?
heliotropic rash
Describe the microscopy of Dermatomyositis
Very similar to lupus : 1. Thin atrophic epidermis, inflammation and destruction of adnexal structures
2. IgG deposited in basement membrane
Often there’s a lot of dermal mucin
Negative Immuno fluorescent test
Describe the presentation of lichen planus
Appears on the flexor surfaces, mucous membranes and genitals of adults
Can last for 1-2 years or longer in the oral cavity
What is lichen planus
A type 4 hypersensitivity reaction
What is lichen planus associated with
Viral hepatitis. HIV and drug use
How do bullous diseases manifest
Manifest as the formation of fluid filled blisters
Name the 2 types of bullous skin diseases
- Pemphigus
- Pemphigoid
What is the difference in Pemphigus and Pemphigoid manifestation
Where the fluid filled blisters form in the epidermis
Where do blisters form in Pemphigus
Blisters form within the epidermis (intra epidermal bulla)
Where do blisters form in pemphigoid
Blisters form at the bottom of the epidermis (sub epidermal bulla)
Describe pemphigus blisters
Quite fragile and can easily fall off
Describe pemphigoid blisters
Quite tense and robust
What type of diseases are bullous diseases
They are autoimmune diseases
Where do antibodies form in pemphigus?
Form in intercellular junctions
Where do antibodies form in pemphigoid?
In the basement membrane
What is pemphigus
It’s a group of disorders characterised by loss of cohesion between keratinocytes resulting in an intraepidermal blister
What do all types of pemphigus cause
Cause fragile blisters/ bullae which rupture easily
Can be extensive and may involve the mucous membrane
Describe the pathogenesis of pemphigus
Autoantibodies are directed against intercellular materials
How can pemphigus be detected
By imminofluoresecence (IMF)
What is bullous pemphigoid
A disease characterised by subepidermal blisters
These blisters are large and tense and down rupture easily
Describe the pathogenesis of bullous pemphigoid
Autoantibodies to glycoprotein in basement membrane that can be detected by IMF
What is dermatitis herpetiformis
Small intensely itchy blisters associated with the deposition of IgA
Who is dermatitis herpetiformis most common in
Young people
What is dermatitis herpetiformis associated with
Coeliac disease
Describe the histopathology of dermatitis herpetiformis
Neutrophil micro-abscesses in dermal papillae
Where do blisters caused by dermatitis herpetiformis form
They form sub epidermally and cause IgA in dermal papillae
Why is it hard to get a biopsy of a blister caused by dermatitis herpetiformis ?
As they are incredibly itchy and people often scratch away at them before they can be inspected
List some skin lesions that are a sign of systemic disease
- Dermatomyositis
- dermatitis herpetiformis
- Ancanthosis nigricans
- Necrobiosis lipoidica
- Erythema nodosum
What can Dermatomyositis a sign of
Can be a sign of visceral cancer
What can dermatitis herpetiformis be a sign of?
Coeliac disease
Describe ancanthosis nigricans
Dark warty lesions in the armpits
What does IMF stand for
imminofluoresecence
What can ancanthosis nigricans be a sign of
Intermal malignancy
Describe Necrobiosis lipoidica
Red and yellow plaque on legs
What can Necrobiosis lipoidica be a sign of
Diabetes melitus
Describe Erythema nodosum
Red tender nodules on the shins
What can Erythema nodosum be a sign of
Associated with infections elsewhere especially lungs
what is pretibia myxedema
what is it associated with
swollenl, tense looking shins
thyroid disease
