Immunology - Inflammatory dermatoses Flashcards
Describe the basic microanatomy of the skin
- Epidermis
- Basement membrane
- Dermis
- Fat
- Fascia
- Muscle
What does the dermis contain
- Hair follicles
- Sebaceous glands
- Piloerector muscles
- Sweat glands
- Collagen
- Elastin
- Fibroblasts
- Immune cells
What is the function of sebaceous glands
They produce and oil that coats hair and prevents bacterial and fungal infections
What are the 5 layers of the skin
- Stratum Corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
What comprises each of the layers of the skin
- Stratum Corneum - dead keratinocytes, no nuclei
- Stratum granulosum - keratin containing granules
- Stratum spinosum - spines between cells = desmosomes
- Stratum basale - merkel cells, melanocytes, dividing keratinocytes
What is the keratinocyte differentiation pathway
Basal cells -> prickle cells -> granular cells -> keratin
What are the functions of the stratum corneum
- Important barrier function of the skin
- Made of corneocytes (differentiated keratinocytes) with lipids and proteins between them
Which one of these proteins can cause a predisposition to eczema
Filagrin (10% of population carry faulty filagrin gene)
What are the three atopic diseases
- Eczema
- Asthma
- Hayfever
Describe the atopic march
- First develop eczema which peaks at 1-2
- Food allergies also peak at 1-2
- Then they develop asthma
- Then they develop rhinitis (hayfever)
How does eczema cause inflammation
Faulty barrier allows entry of irritants, allergens and pathogens
What is a sign of a filagrin gene mutation
Palmar hyperlinearity
Describe infantile ectopic eczema
- Acute eczema - red, raw, weepy, blistering skin, poorly defined edges
- Often in areas that baby can reach and rub e.g. face, elbow, knees
How does the pattern of atopic eczema change with age
In adults it occurs in more flexual areas that are sweatier and rub more
What is the visual difference between acute and chronic eczema
Chronic eczema is more skin colour and skin markings are more visible due to scratching/rubbing of the skin
Describe an example of severe eczema
Eryhtrodermic eczema
- Red all over as well as general unwellness
- Usually needs hospital admission
- Usually caused by staphylococcal superinfection
Describe the cause, appearance and possible effects of eczema herpeticum
- Herpes simplex infection due to impaired barrier function of the skin
- Small blisters that then break down to form small ulcers
- If it is extreme it can enter the bloodstream and cause herpes encephalitis
What causes seborrheic eczema and describe the presentation
- Caused by an overgrowth of yeast
- Greasy scale with redness often around nose, eyes and scalp (dandruff on scalp)
What is allergic contact dermatitis
- Allergy to a specific product
- Atopic eczema predisposes to allergic contact dermatitis
- Could be caused by perfume, fragrances, nickel, rubber, topical treatments (steroids/antibiotics)
What is PPD
It is a black dye that is sometimes used in henna but is banned in the UK as it causes a sensitisation when it is directly injected into the skin, meaning that it causes allergic reactions when used in other products such as hair dye
What is discoid eczema
- Circular discs of redness
- Caused by overwashing
- Treated with topical steroids
What does the presentation of psoriasis look like
Raised, salmon pink, well defined plaques with a silvery scale
What causes psoriasis
It requires a genetic susceptibility for which there are several genes and then there needs to be an environmental trigger
What is the pathology of psoriasis
T cells predominate in dermis stimulating cytokine release causing neutrophils to enter the dermis causing overproduction of keratinocytes which thickens the epidermis
Describe the histology of psoriasis
- Hyperkeratosis - reddening on skin
- Acanthosis - thickening of epidermis
- Parakeratosis - retention of nuclei in keratinocytes
Describe the presentation of guttate psoriasis
- Lots of small raindrop popules of psoriasis
- Often affects young people after streptococcal infection
- Recurrent guttate psoriasis with recurrent tonsillitis can be treated with removal of tonsils
What is palmoplantar pustulosis
Formation of pustules on the palms of hands and soles of feet
- predisposed by smoking
What is generalised pustular psoriasis
- Plaques and widespread superficial small pustules
- Background of inflamed skin
- Patient often unwell, malaise, tachycardic
- Treated with immunosuppressants
What does acne effect
The pilo-sebaceous unit (pilo erector, hair follicle, sebaceous gland)
What is an effective treatment for acne and what must be monitored
Accutane - very effective treatment but can be teratogenic and requires monitoring of depression and cholesterol
What is the pathogenesis of acne
- Hyperkeratinisation of the epidermis in the infundibulum of hair follicles (comedone) -leads to accumulation of dead keratinocytes wihtin the hair follicle
- Increase sebum production stimulated by androgens.
- Proliferation of Propionibacterium acnes within pilosebaceous unit.
- Rupture of inflamed pilosebaceous unit causes further inflammation of surrounding skin.
Describe the clinical features of acne
- White head is the closed comedone
- Black head is the open comedone where you can see the dead keratinocytes
- papule is a raised lesion
- Pustule is when you can see pus
- Nodule is a thickening of the skin
Describe the pathogeneis of bullous pemphigoid
- Autoantibody against a component of the basement membrane
- Causes splitting of the basement membrane which causes blistering
What proteins hold the dermis and epidermis together
- Tonofilaments
- Anchoring fibrils
What is the treatment for bullous pemphigoid
Steroids suppress the immune attack allowing the skin to recover
What causes epidermolysis bullosa
A genetic fault in one of the proteins that hold the basement membrane together
Describe the pathogenesis of pemphigus vulgaris
Autoantibodies against desmosomes connecting the keratinocytes together
Describe the clinical presentation of pemphigus vulgaris
- More superficial than bullous pemphigoid
- Easily breakable superifical blisters that appear as erosions
