Inflammatory dermatoses Flashcards
What are the 3 layers of the skin?
Epidermis
Dermis
Hypodermis
What is dermatitis also known as?
Eczema
What are the different types of eczema?
Atopic
Seborrhoeic
Discoid
Allergic contact
What is the definition of atopy?
Tendency to develop hypersensitivity
What is atopic eczema?
Very common itchy skin condition
What is the onset of atopic eczema like?
It is often within first 6 months of life. Many children grow out of it but a proportion doesn’t
What is the biology of eczema?
Defective barrier function of the skin leading to dry skin
What is mutated in 10% of eczema cases?
Filagrin gene
What is filagrin?
Epidermal protein important in maintaining barrier function of the skin
What does defective barrier function in eczema allow?
Penetration of irritants, allergens (e.g. house dust mite particles) and pathogens e.g. staph aureus. Inflammation of the skin then occurs
What is seborrhoeic eczema?
Very common type of eczema affecting babies and adults, often not itchy
What is the pathology of seborrhoeic eczema?
There is overgrowth of malassezia species of yeast on the skin with associated skin inflammation.
What is distinctive in seborrhoeic eczema?
The rash has a distinctive distribution including nasolabial folds, eyebrows, scalp, central chest and sometimes axillae and groins
What is psoriasis?
Another common inflammatory dermatosis
When does psoriasis usually start?
Teens or 40s/50s
What are the different types of psoriasis?
Chronic plaque
Guttate
Palmoplantar pustulosis
Generalised pustular psoriasis
What percentage of patients with cutaneous disease are affected by psoriatic arthritis?
Approximately 30%
What are the underlying cause of psoriasis?
Genetic susceptibility and environmental triggers- many genes are implicated including PSOR1
What is the pathophysiology of psoriasis?
Immune process occurs where T lymphocytes move out of blood vessels into the dermis and initiate the release of cytokines e.g. tumour necrosis factor alpha. The epidermis becomes thickened and produces more keratinocytes than normal, neutrophils infiltrate the epidermis and lymphocytes infiltrate the dermis
What triggers for psoriasis are there?
Infections
Drugs
Stress
Who is mainly infected by acne?
A very common condition which mainly affects teenagers and young adults
What is the biology of acne?
It is disease of the pilosebaceous unit of the skin
What is the pathogenesis of acne?
It is multifactorial and includes:
Hyperkeratinisation of the epidermis in the infundibulum of the hair follicles
Accumulation of dead keratinocytes in lumen of the hair follicle
Increased sebum production stimulated by androgens
Proliferation of propionibacterium acnes within the pilosebaceous unit
Rupture of the inflamed pilosebaceous unit with further inflammation of the surrounding skin
What are the key clinical features of acne?
Open and closed comedones Papules Pustules Nodules Scars on face, chest and back
What is bullous pemphigoid?
An autoimmune bullous inflammatory condition most common in the elderly
What are the clinical features of bullous pemphigoid?
Intense pruritus followed by development of tense blisters on an erythematous background of skin or mucous membranes
What is the biology of bullous pemphigoid?
IgG antibodies to basement membrane antigens BP180 or BP230 result in cleavage of skin at the demo-epidermal junction leading to sub-epidermal blisters
What is pemphigus vulgaris?
An uncommon autoimmune bullous inflammatory disease which usually affects middle aged individuals
What do the clinical features of pemphigus vulgaris include?
Flaccid blisters which easily break leaving erosions and crusted lesions
What is the biology of pemphigus vulgaris?
IgG autoantibodies to epidermal cell surface proteins desmoglzins 1 and 3 lead to loss of cell-cell adhesion within the epidermis causing flaccid blisters in the skin or mucous membranes
