Lecture 22: Skin Conditions Flashcards
What are the two main layers of the skin?
- Epidermis
- Dermis: oil gland, nerve, sweat gland
What are the functions of the skin?
- Barrier to water
- Controls temperature
- Sweat glands control fluid balance
- Nerve endings control sensations
- Langerhans and dendritic cells involved in immunological defence
- Protection from UV through melanocytes
What is terminal differentiation?
Keratinocytes differentiate and die by losing thier nucleus to become outer skin
What are the four layers of the skin?
- Basal - proliferation
- Spinous - Early differentiation
- Granular - Late differentiation
- Cornified - cornification
How do disease conditions stop skin differentiation?
It takes 28 days for keratinocytes to become the cornified layer. Interuption to this process means terminal differntiation is not complete. So we have proliferating keratinocytes as your cornified layer. They are leaky, dry and not smooth as they dont express the right proteins
Describe the inflammatory component of skin conditions
- Inflammation causes the influx of white blood cells. This causes release of inflammatory mediators (eg IL1, TNF alpha and PGs). This promotes proliferation and keratinocytes dont terminally differentiate. This increases blood flow which causes redness, and swelling due to capillary leakiness and itch and pain.
Describe the immunology involved in skin conditions
The innate immune system recognized parts of the infectious agent through pattern recognition receptors on white blood cells, endothelial cells etc. Activation of PRR initiates the inflammatory response and passes the recognition onto the adaptive system. The adaptive system generates T and B cells which fights the infectious agent
What is the general pharmacology used for skin conditions?
- Emollients: Provide a layer of oil to slow water loss. They increase water holding capacity and act as a lubricant
- Directly attack the cause eg infections
- Combat inflammation
- Attack the immone problem eg cytokines or immune cells
What is the treatment for seborrheic dermatitis?
- Antifungal cream: ketoconazole
- Topical corticosteroid for inflammtion
- Medicated shampoo: Ketoconazole or coal tar extract to cut down inflammation
What is psoriasis?
A chronic, relapsing and remitting papulo squamous skin disease which can appear on any part of the skin eg knees, elbows, scalp, back. It may be initiated by hypertension, obesity, smoking, alcohol, mental health. It is T cell mediated. Th1 cells secrete cytokines TNF alpha, IL1B and IL6. Dendritic cells release IL12 to direct CD4+ T cell to TH1. The inflammation causes keratinocytes to proliferate. Keratinocytes also release inflammatory mediators
What are the topical treatments for psorosis?
- Anti-inflammatory topical agents: Corticosteroids, retinoids (Tazorten)
- Slowing skin cell growth: Vitamin D analogues (calcipotirol), Dithranol
- Reducing scaling/ itching: emollient, coal tar
What is the treatment for severe psoriasis?
- Narrowband UVB light: converts TH1 to TH2
- Systemic ciclosporin/ Cyclosporin: A calcineurin inhibitor, stops IL2 production in CD4+ T cells, this stops proliferation and expansion of T cells
- Systemic methotrexate: To kill T cells and dendritic cells
- Biologics: Injected into skin, Imfliximab/ Adalimumab, etanercept, Ustekinumab
What is infliximab/ Adalimumab against?
Anti TNF alpha antibodies
What is etanercept against?
TNFa receptor fusion protein - gets rid of TNF alpha
What is ustekinumab against?
IL12/ IL23 antibody
What is dermatitis and the types?
Patches of skin that are itchy, dry, cracked and sore. The types are atopic dermatitis, non allergic contact dermatitis and contact allergic dermatitis
What is the immunology of atopic dermatits?
It is a TH2 disease. Type 2 helper CD4+ cells in the skin stimulate B cells to make IgE
What is the immunology of allergic contact dermatitis?
Adaptive immune response to allergen. TH1 release TNF alpha. Slow onset 24-48 hr
What is the underpinning immunology of non allergic contact dermatitis?
Irritant damages the skin - may also cause inflammation
What is the treatment for atopic dermatitis?
- Topical steroids for inflammation
- Tacrolimus: Calcineurin inhibitor, stops T cell proliferation
- Systemic: Methotrexate, clyclosporin
- Tralokinumab: IL13 antibody - CD4+ cells release IL13 to stimulate B cells
What is the treatment for contact allergic dermatitis?
- Emollients
- Topical steroids
- UV therapy
- Tacrolimus
- Allergen patch test to avoid allergan
What is the treatment for non allergic contact dermatitis?
- Remove from irritant
- Lotions
- Topical steroids
- Antihistamine only for sedative effect
What is rosacea?
Usually face redness due to capillary dilation on forehead, nose and cheeks, pimples, swelling and superficial dilated blood vessels
What is the treatment for rosacea?
- Topical ivermectin (insecticide and act-helminthic kills mite)
- Long term systemic antibiotics (Metronidazole/ oxyteratracycline)
- Severe rhinophyma - Surgery
What is the treatment for rosacea?
- Topical ivermectin (insecticide and act-helminthic kills mite)
- Long term systemic antibiotics (Metronidazole/ oxyteratracycline)
- Severe rhinophyma - Surgery
What is impetigo?
Superficial infection by staphylococcus aureus or streptococcus pyogenes. It is rare, except in poor hygiene. It spreads quickly. The clinical features are honey crust on the face and hands.
How is impetigo treated?
- Remove the crust using saline, olive oil
- If superficial use topical antibiotic fusidic acid
- If systemic use penicillan/ flucloxacillin, erythromycin (also to prevent streptococcal nephritis)
- If mild use 1% hydrogen peroxide cream
How does a virus get in the body and lead to infection?
Virus gets into body from respiratory tract and is recognized and engulfed by dentritic cells. The dentrictic cell takes it to a lymph node. It gets presented to a T cell. The infected T cell goes to the skin and presents the virus to cause lesion and inflammation. T cell also goes to dorsal route ganglia – the virus lays dorment there and becomes reactivated after many years.
What are the symptoms linked to inflammation from a virus?
- Itching
- Pustules
- Dry blisters
- Fevere
How does shingles occur?
Virus lies dormant from childhood and breakouts in nerve endings from the spine - much more painful (neuralgia) than adult chickenpox
How does shingles occur?
Virus lies dormant from childhood and breakouts in nerve endings from the spine - much more painful (neuralgia) than adult chickenpox
How is the innate and immune system involved in Chickenpox and Shingles – varicella zoster virus?
Interferons to limit the spread (innate) and B-cells to make antibodies and T-cells (CD8) to kill virus directly (again to limit the spread)
What is the treatment for Varicella zoster virus?
- Analgesics: Paracetamol for high temperature/ pain. Not NSAIDs
- Soothing drying lotions for the rash: Calamine lotion (Zinc oxide)/ cooling gel
- No topical steroids
- Anti-histamine for itch
- For more severe adult chickenpox/ shingles: Antiviral agents - Aciclovir needs to be given early (24-48 hours from rash onset)
- Vaccine only given to susceptible individuals
Describe the mechanism of a fungal infection
- Uses hyrolytic enzyme such as aspartic proteased and lipases to bury into the skin or nails
- Dendritic cells ingulf both yeast part and the hyphae
- The yeast part mediates a TH1 response and the hyphae part a TH2 with different cytokine profiles
- Often neutrophils and macrophage (as part of the innate response) –clear an initial infection and you don’t notice
Describe lice and the treatment
- Pediculosis corpus infestation
- Wet combing, Hedrin (Dimeticone which drowns the lice
- Permethrin lotion - an insecticide
What is scabies and its treatment?
- sarcoptes scabei mite infestation.
- Female mite buries into top layer of the skin and lays eggs
- Allergic reaction to the mite: Th2, IgE and longer term T cell reaction
- Causes a severe itch in the fingers and body folds, feet in babies
- Treatment is permethrine lotions all over the body
- Oral ivermectin an insecticide
- In babies 2.5% sulpher ointment
