What cells are found in the stratum basale?
- merkel cells
- melanocytes
- dividing keratinocytes
What is the keratinocyte differentiation pathway?
basal cell -> pricle cell -> granular cell -> keratin
What are the types of eczema?
- Atopic
- Seborrhoeic
- Discoid – occurs in small discrete discs
- Allergic contact
What are the features of atopic eczema?
“the tendency to develop hypersensitivity” – includes eczema, hay fever & asthma:
- Very common, itchy skin condition with onset from first 6 months of life. Many grow out of it
Cause : defective barrier of skin
then allows entry of irritants, allergens and pathogens which then cause inflammation.
- Filagrin (an epidermal protein) gene mutation in ~10% of patients
> Palmar hyperlinearity is a sign of the mutation.
What are the features of seborrhoeic eczema?
- Common skin condition affecting babies and adults but is NOT itchy
- Associated with an overgrowth of malassezia (species of yeast on the skin that causes inflammation)
- The rash has a distinctive distribution involving – nasolabial folds, eyebrows, scalp, central chest, axilla and groin
What are the types of psoriasis?
- Chronic plaque
- Guttate
- Palmoplantar pustulosis
- Generalised pustular psoriasis – same as above just everywhere
What are the causes of psoriasis?
- Genetic susceptibility – many genes are implicated including PSOR1
- Environmental causes
*Triggers include infections, drugs and stress
Describe the pathophysiology of psoriasis
T-lymphocytes move out of blood vessels into the dermis and initiate release of cytokines (e.g. TNFa). The epidermis thickens in response (produces more keratinocytes). Neutrophils infiltrate the epidermis and lymphocytes infiltrate the dermis
Describe the pathogenesis of acne
disease of the pilosebaceous unit of the skin
multifactorial:
- Hyperkeratinisation of the epidermis in the infundibulum of hair follicles - Accumulation of dead keratinocytes in the lumen of the hair follicle
- Increase sebum production stimulated by androgens
- Proliferation of Propionibacterium acnes within pilosebaceous unit
- Rupture of inflamed pilosebaceous unit -> further inflammation of surrounding skin
What are the clinical features of acne?
- open (blackhead)/closed (whitehead) comedones
- papules
- pustules
- nodules and scars on face, chest and back
What is bullous pemphigoid?
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 membrane – E.G. Epidermolysis bullosa
Describe the pathogenesis of bullous pemphigoid
IgG auto-antibodies against basement membrane antigens BP180 (T17 collagen) or BP230 result in cleavage of skin at the dermo-epidermal junction leading to sub-epidermal blisters
What is pemphigus vulgaris?
uncommon AI bullous inflammatory disease most common in middle-aged people
- Clinical features – flaccid blisters which break easily leaving erosions and crusted lesions
What causes pemphigus vulgaris?
o IgG auto-antibodies to epidermal cell surface proteins desmogleins 1 & 3 -> loss of cell-cell adhesion (acantholysis) within the epidermis causing flaccid blisters in the skin or mucous membranes
