Aetiology of skin conditions - other skin lecture is more important this one don't need to know in too much detail

How long is cell turnover?

28 days - longer cycles as you age

What are the layers of the Skin structure and what seperates these layers

-epidermis: thin tough outer layer, prevents loss of water and body fluids and acts as protective layer, thickness depends on part of the body

-dermis - elastic tissue, where collagen, elastin and fibrinogen are = flexibility and stretch of skin, decompromises as you get older. Also contains nerve ending s

-Subcutaneous tissue - Fatty layer that insulates body and acts as padding and energy storage

What is Psoriasis ?

• Chronic inflammatory skin disease

• Increased epidermal cell turnover = thickening and scaling

• Inflammatory cell infiltration

• Relapsing / remitting

Note : affects men and women the same

BIG HINT THIS PART WILL BE IN THE EXAM AS A CASE QUESTION: What is the cause of Psoriasis?

Immune mediated antigen → T cell activation → release of inflammatory cytokines (e.g. IL 23 or 17 etc.) - these are updriven in psoriasis→ epidermal hyper proliferation = Plaques

-Genetic factor also

What else can trigger Psoriasis (what are the precipitating factors)?

• Injuries such as cuts, abrasions, sunburn

• Streptococcal infection

• Hormonal events – often improves during pregnancy and relapses in the postpartum period

• Sunlight – usually improves but 10% will get worse

• Drugs (beta-blockers, lithium, NSAIDS, antimalarials, withdrawal of systemic steroids) - KEY FOR THE EXAM!!!!!

• Alcohol

• Smoking

• Stress

-Obesity

What area the different types of Psoriasis ?

MAIN ONE: CHRONIC PLAQUE PSORIASIS

-Plaque = thickened/raised patch > 2 cm across

• Red plaques – well defined edge covered with silvery scales

• Plaques can be any size • Scale = flakes of stratum corneum, accumulate or shed

• Can affect any area (usually scalp, kness/shins, outside of elbows, lower back)

• Plaques can crack and bleed – scratching/removing scales → pinpoint bleeding

-usually symmetrical in distribution across the body

Guttate Psoriasis:

-Acute

-children and young adults usually

-often after a streptococcal throat infection

-Multiple, small, pink, scaly drop-like plaques over trunk + limbs

FLEXURAL PSORIASIS

-Affects skin folds e.g. armpits, groin, under breasts

-Shiny and moist

-Prone to secondary infection

What is the difference between eczema and dermatitis ?

-Eczema is endogenous caused

-Dermatitis is cause by exogenous factors e.g. allergic or irritant contact dermatitis

What is eczema and what is it caused by ?

• Impaired barrier function of skin

•Filaggrin is considered a major genetic risk factor for eczema because mutations in the filaggrin gene (FLG), a protein,= defect in production of lipids that normally holds keratinocytes firmly together or over activity of immune system. lead to a weakened skin barrier, making individuals more susceptible to developing the condition; essentially, a deficiency in filaggrin protein disrupts the skin's ability to retain moisture, leading to dry, itchy skin which is a hallmark of eczema

• Causes water loss, dry cracked & itchy skin

Note:

causes Easier entry of irritants and allergens cause an inflammatory response and infections

-can be acute or chronic

What is atopic eczema ?

-a genetic tendency to develop allergic diseases e.g. eczema - affects children mostly

-Asymmetrical appearance

-Red skin, scratched bleeding

- Suggested due to immature immune system and high IgE levels (also in asthma

-Precipitate factors:

- Dry skin - Stress - Extremes of temperature - Infection

What is allergic contact dermatitis??

-External factor = allergic dermatotic response, Allergy to usually harmless substances that have been in contact with the skin e.g. creams or fragrances

-Visible in 48/96 hours after contact with allergen

-Patch testing can be useful in patients

Cause:Activation of T-cells → release of cytokines

Questions to ask patient with suspected allergic contact dermatitis

area affected, timing, exposure?

What is irritant contact dermatitis?

-similar but not the same as allergic- No allergy involved

-Caused by substance which are irritant to skin - chemical/mechanical irritation e.g. hand soap

What do irritants do ?

Irritants remove oils and lipids from stratum corneum → deeper penetration of irritant → triggers inflammation

What is acne ?

-inflammation of the sebaceous glands in the skin

-usually affects face/back/chest - where sebaceous glands most numerous and active

How do we assess severity of acne ?

• Mild = non-inflam, <20 comedones

• Severe = extensive nodular cysts, scarring, >125 lesions

What are the types of acne and their symptoms?

Symptoms of acne in general:

• Greasiness • Comedone formation

Blackheads:

•Small open follicular papules containing a central black keratin plug •Pigmenation from oxidised melanin (not dirt)

Whiteheads:

• Small closed follicular papules

• no visible central keratin plug

Pathogenesis of Acne

-Driven by sebaceous glands

-Bigger sebaceous glands can cause an increased activity by androgens (hormones) that effect the formation of comodones as more sebum is being produced

-Keratin plugs stop the outflow of the sebum produced by the sebaceous glands = build up of sebum comodone formation