Lecture 4 - skin conditions Flashcards
What are the three layers of the skin?
Epidermis (outer layer), Dermis (middle layer), Hypodermis (bottom subcutaneous layer)
What are the 7 functions of the skin?
Protection, Sensation, Regulates temperature, Stops water loss, Makes vitamin D, Fights germs
Describe the process of keratinocytes differentiation.
In the basal layer (stratum basale), keratinocytes are created and start making keratin. As they move up through the spinous layer (stratum spinosum), they form desmosomes. In the granular layer (stratum granulosum), they release lipids. In areas like palms and soles, they pass through the clear layer (stratum lucidum). Finally, in the cornified layer (stratum corneum), they become flat, dead cells filled with keratin.
How long does it take for keratinocytes to mature and form the cornified layer?
28 days
What happens if the keratinocyte differentiation process is disturbed?
Keratinocytes become leaky, dry, weak, and cannot produce the right proteins, leading to rough skin texture and increased susceptibility to infection and inflammation.
What are some skin conditions that can develop from disturbed keratinocyte differentiation?
Psoriasis, Dermatitis
Briefly describe the process of inflammation in the skin.
white blood cells release cytokine and chemokines to trigger more white blood cells so that they can end up attacking the keratinocytes of the skin causing them to proliferate
What does inflammation of the skin normally cause?
Redness, Swelling, Pain, Increased itching
Describe the innate response. (Psoriasis)
The white blood cells in the skin have special receptors called Pathogen Recognition Receptors that identify the kertainocyted as foreign and release cytokines to further recruit more immune cells to bring about inflammation.
What does the adaptive immune system do when notified?
It generates specific T and B cells to fight the invader.
What subsets of T cells are involved in the immune response?
TH1, TH2, TH11, TH17
What do emollients do to the skin?
Provide a layer of oil that acts as a barrier, keeping moisture in.
What is the role of occlusion in skin care?
Occlusion slows down water loss from the skin by providing a layer of oil.
How do humectants benefit the skin?
Humectants increase the skin’s ability to hold water, helping retain moisture.
What does lubrication do for the skin?
Lubrication allows the skin to glide more easily, reducing friction and irritation.
How can we help the skin?
Provide emollients, directly tackle the cause, and combat aspects like inflammation and dryness.
What is psoriasis?
Psoriasis is a chronic, relapsing-remitting papulo-squameous skin condition that can affect any part of the skin.
What is the incidence of Psoriasis and is it different in males and females?
The incidence is 1-2% and is similar in both males and females.
Which areas of the skin does psoriasis most commonly affect?
Knees, elbow, scalp, back
What conditions can arise as a result of psoriasis or make it worse?
Hypertension, Obesity, Smoking, Alcohol, Mental health
Describe the pathology of psoriasis.
Dendritic cells release IL-12 to stimulate CD4+ T cells, leading to inflammation and rapid proliferation of keratinocytes.
What are common topical treatments for skin conditions?
Emollient, Cold tar, Dithranol, Corticosteroids, Tazarotene, Vitamin D analogues
What is the function of emollients?
Occlusion, Humification, Lubrication
What does cold tar do?
Reduces inflammation.
What does dithranol do?
Inhibits proliferation of keratinocytes.
What do corticosteroids do?
Reduce inflammation and treat flare-ups.
What do Tazarotene and Vitamin D analogues do?
Help reduce proliferation, increase differentiation, and reduce inflammation.
What are some more severe treatments used in psoriasis?
- Narrowband UVB light
- Systemic treatments
Ciclosporin (IL 2 inhibitor in T cells)
Methotrexate
3 . Biologics (injected into the skin)
infliximab, adalimumab
Etanercept
Ustekinumab
Explain how Narrowband UVB light helps treat psoriasis.
It shifts the TH1 mediated condition into a TH2 mediated condition, suppressing inflammation.
How does cyclosporine treat psoriasis?
Stops T cells from proliferating and producing IL-2.
How does methotrexate treat psoriasis?
Kills T cells and dendritic cells, inducing apoptosis.
How do biologics help treat psoriasis?
They inhibit certain cytokines released from CD4+ T cells.
What is dermatitis?
Patches of skin that are dry, itchy & flaky.
What are the different types of dermatitis?
Atopic dermatitis, Contact (allergic/irritant) Dermatitis, Seborrheic dermatitis
What triggers atopic dermatitis?
Genetic makeup, cold air, stress, inhalation of allergens.
What triggers contact dermatitis (irritant)?
Direct damage from irritants like soaps, detergents, or chemicals.
What triggers contact allergic dermatitis?
Something touching the skin, like jewelry or latex.
What triggers Seborrheic Dermatitis?
Overgrowth of yeast on the epidermis.
Briefly explain the pathogenesis of Atopic dermatitis (eczema).
CD4+ T cells differentiate into TH2 cells, which recruit B cells that release IgG antibodies.
What TH cells might cause atopic dermatitis in Asian populations?
TH17
Briefly explain the pathogenesis of allergic contact dermatitis.
Nickel is absorbed through the skin, stimulating TH1 cells which remember the allergen for future reactions.
What is the name given to the reaction in allergic contact dermatitis?
Type IV delayed hypersensitivity.
What are three things we must know about irritant contact dermatitis?
Caused by direct damage, can cause inflammation, and has periods of symptom relief.
What are some treatments used for atopic dermatitis?
Topical steroids, Tacrolimus, Methotrexate, Ciclosporin, Tralokinumab
What are some treatments used for contact allergic dermatitis?
Emollients, Topical steroids, UV therapy, Tacrolimus
What are some treatments used for contact irritant dermatitis?
Remove irritant, Lotions, Topical steroids
Why are antihistamines not used for dermatitis?
Not effective and cause sedation.
Define impetigo.
Skin infection caused by bacteria - staphylococcus aureus & streptococcus pyogenes.
Which population does impetigo occur in?
Children and people with poor hygiene.
What does impetigo look like?
Honey crust on face & hands.
What is recommended for impetigo treatment?
Remove crusts using saline solution or olive oil.
What would you recommend if the impetigo is superficial?
Topical antibiotics - fusidic acid.
What would you recommend if the impetigo was deeper?
Oral antibiotics - penicillin/flucloxacillin or erythromycin.
When else might erythromycin be good to use?
For streptococcal nephritis.
If a patient has a mild case of impetigo and you are reluctant to use antibiotics, what could be used instead?
1% hydrogen peroxide cream.
What is the difference between chickenpox & shingles?
Chickenpox are small, red bumps all over the skin, while shingles is a painful rash usually on one side of the body.
What virus causes chickenpox & shingles?
Varicella zoster virus.
How does VZV infect the skin?
It enters the respiratory system and travels through the bloodstream to the skin.
Briefly explain the pathogenesis of chickenpox/shingles.
VZV is inhaled, travels to skin cells, replicates, and can later reactivate in nerve cells.
What is used to treat VZV?
Paracetamol, Calamine lotion, Piriton.
What can be used to treat severe cases of chickenpox in adults or shingles?
Aciclovir, vaccinations.
What are candida albicans?
A fungal infection that causes red, itchy rashes due to overgrowth of yeast.
What enzyme does the candida albicans fungus use to penetrate the skin?
Hydrolytic enzymes like aspartic proteases and lipases.
How do dendritic cells respond to fungal infection?
They engulf both the yeast and the hyphae of the fungus.
What immune response does the yeast part of the fungus initiate?
A TH1 response.
What immune response does the hyphae part of the fungus initiate?
A TH2 response.
Which cells clear an initial fungal infection?
Neutrophils and macrophages.
What is the treatment for candida albicans?
Clotrimazole 1% cream.
How can you distinguish between a bacterial, fungal, viral skin condition?
By evaluating symptoms, appearance, and response to treatments.
What is pediculosis corpus infestation?
An infestation of lice on the head, body, or pubic areas.
Who is most commonly affected by pediculosis?
Children.
What cells clear an initial fungal infection?
Neutrophils and macrophages (as part of the innate immune response).
What is the treatment that can be used for candida albicans (fungal skin infections)?
Clotrimazole 1% cream.
How can you distinguish between a bacterial, fungal, viral skin condition?
HEAD LICE.
What is pediculosis corpus infestation?
An infestation of lice on the head (capitis) or body or even the pubic areas (pubis).
Who is most commonly affected by pediculosis?
Children and vagrants (people that don’t have a permanent home).
What are the clinical features of pediculosis infestation?
You might see itchy “dots” on the hair, louse eggs (nits) on the hair, and dermatitis from bites.
What are the treatments for pediculosis?
Hedrin shampoo and Permethrin lotion (neurotoxin) to kill lice, used with a wide tooth knit comb.
What are scabies?
This is a skin condition caused by tiny mites called Sarcoptes Scabiei.
How does scabies spread?
From close skin-skin contact, often in crowded environments.
How is scabies caused?
The female mite burrows into the top layer of skin (epidermis), lays their eggs, and has a 14-day cycle.
What type of immune response is triggered by scabies?
An allergic TH2 cell response - IgG production - longer term T cell reaction.
Explain briefly what a longer term T cell reaction looks like?
Longer-term T-cell response involves T-cells recognizing the scabies mites more specifically over time.
What are the common features of scabies in infants and children?
Severe itching, often in the fingers, body folds, and feet, with lesions sometimes appearing in lines.
What is the standard treatment for scabies?
Permethrin lotion (applied from head to toe for 24 hours) and oral ivermectin.
What treatment is recommended for scabies in babies?
2.5% Sulphur ointment, which is very safe for babies.
