Dermatology Flashcards
What are the key functions of the skin?
Barrier to infection Thermoregulation Protection against trauma Protection against UV Vitamin D synthesis Regulate H2O loss
Where does normal proliferation of the skin ovvur?
In the basal layer
What is desquamation?
Shedding of mature corneocytes from the skins surface to balance the introduction of new cells.
What is the pH of the skin?
5.5
What causes desquamation?
Degradation of the extracellular corneo-desmosomes under the action of protease enzymes
What are the 3 main layers of the skin?
Epidermis (top layer
Dermis
Hypodermis (Subcutaneous fat)
What does the epidermis consist of?
Layers of keratinocytes undergoing terminal maturation.
Non-keratinocyte cells: Melanocytes, Langerhans cells, Merkel cells
What is the stratium corneum and what does it consist of?
The outermost part of the epidermis.
Made up of corneo-desmosomes (adhesion molecules) and desmosomes which keep the corneocytes together (brick and iron rod model)
What are corneocytes?
Terminally differentiated keratinocytes that compose most of the stratum corneum.
What is the action of melanocytes?
Responsible for melanin production and pigment formation
What is the action of Langerhans cells?
Antigen-presenting dendritic cells
What is the action of Merkel cells?
Sensory mechanoreceptors.
What is cornification?
Differentiation of keratinocytes into corneocytes (dead cells) to create a physical barrier for the skin.
What are the layers of the epidermis?
Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum
How long does a keratinocyte typically take to travel from the stratum basale to the stratum corneum of the epidermis?
30-40 days
What are the layers of the dermis?
The superficial papillary layer and the deeper reticular layer
What are the features of the reticular layer of the dermis?
Thick with thick bundles of collagen fibres that provide more durability.
What structures are present in the dermis?
Fibroblasts Mast cells Blood vessels Cutaneous sensory cells Skin appendages
What are the actions of fibroblasts in the dermis?
Synthesise the extracellular matrix
What are the different types of skin appendages?
Hair follicles
Nails
Sebaceous and sweat glands.
Where are the skin appendages derived from and where do they present?
Derived from the epidermis and descend into the dermis during development.
What are holocrine secretions?
Mode of secretion by exocrine glands: Secretions are produced in the cytoplasm and released by the rupture of the plasma membrane which destroys the cell and releases the product into the lumen.
What is the hypodermis?
The tissue immediately deep to the dermis that is major body store of adipose tissue.
What are Meissner’s corpuscles and where are they?
Mechanoreceptors that can sense light touch.
Found in upper dermis
What are Pacinian corpuscles and where are they?
Receptors responsible for pressure and vibration found in the deep dermis
What are the most common causes of itch with rash?
Urticaria (hives)
Atopic eczema
Psoriasis
Scabies
What are the most common causes of an itch with NO rash?
Renal failure Jaundice Iron deficiency Lymphoma (Hodgkins) Polycythaemia Pregnancy Drugs Diabetes Cholestasis
What are pilosebaceous units?
Dimples in the skin the contain hair follicles and sebaceous glands.
What do sebaceous glands produce and how?
Natural skin oils and sebum via holocrine secretion into the hair follicle shaft.
What causes acne?
Increased production of sebum, trapping keratin (dead skin cells) and causing blockage of the pilosebaceous unit, leading to swelling and inflammation.
What increases the production of sebum?
Androgenic hormones (why it is exacerbated by puberty)
What are swollen/ inflamed units of acne called?
Comedones.
What bacteria is thought to play a role in acne and how?
Propionibacterium acnes bacteria–> colonises the skin and excessive growth is thought to exacerbate acne.
What is the key presentation of acne?
Red, inflamed, sore spots on skin, typically across face, upper chest and upper back.
Can vary greatly in severity.
What are
- Macules
- Papules
- Pastules?
- Macules= flat marks on the skin
- Papules= small lumps on the skin
- Pastules= small lumps containing yellow pus
What are the steps in acne treatment?
- No treatment if mild
- Topical benzoyl peroxide
- Topical retinoids
- Topical antibiotics
- Oral antibiotics
- Oral contraceptive pill
- Oral retinoids (e.g. isotretinoin)
What is the action of topical benzoyl peroxide?
Reduces inflammation, helps unblock the skin and is toxic to P.acnes bacteria
What is the action of topical retinoids?
Slow the production of sebum
Why do women of childbearing age need reliable contraception when taking retinoids?
They are highly teratogenic (cause birth defects)
What is the most common variant of acne?
Acne vulgaris.
What is eczema?
A chronic atopic condition caused by defects in the normal continuity of the skin barrier, causing inflammation of the skin.
How and when does eczema usually present?
Usually presents in infancy with dry, red, itchy and sore patches of skin over the flexor surfaces (inside of elbows and knees) and on the face and neck. Usually get flares.
What is the other name for eczema?
Dermatitis
What causes eczema?
Defects in the skin barrier allow entrance to irritants, microbes and allergens that create an immune response, resulting in inflammation and symptoms.
How is eczema managed?
Emollients to create artificial skin barrier
Avoid activities that break down skin barrier (e.g. hot water, scrubbing skin, soaps and body washes)
Avoid environemental triggers
How can eczema flares be treated?
Thicker emollients
Topical steroids
Wet wraps (covering affected areas in emollient and applying wrap to keep moisture locked in overnight)
What is the general rule with emollient treatment?
Use emollients that are as thick as can be tolerated/
What is the general rule with topical steroids to treat eczema?
Use the weakest steroid for the shortest period required to get the skin under control.
What are the risks with using topical steroids?
Can lead to thinning of the skin, which makes it more prone to flares, bruising, tearing, stretch marks and telangiectasia. There may also be systemic absorption of the steroid.
What is the steroid ladder from weakest to most potent?
Mild: Hydrocortisone
Moderate: Eumovate
Potent: Betnovate
Very potent: Dermovate
What are the main complications of eczema?
Opportunistic bacterial infection (e.g. Staph. aureus) Eczema herpeticum (viral skin infection caused by herpes simplex virus)
What are the two types of eczema?
Endogenous–> atopic (due to hypersensitivity)
Exogenous–> Contact dermatitis usually precipitated by chemicals, sweat and abrasives
What is psoriasis?
Chronic inflammatory autoimmune condition that causes skin lesions due to hyper-proliferation of keratinocytes and inflammatory cell infiltration.
What is the appearence of psoriasis?
Patches of dry, flaky, scaly, faintly erythematous (red) skin lesions that appear in raised and rough plaques.
Where does psoriases typically present?
Over extensor surfaces of elbows and knees and on scalp.
What causes the skin changes in psoriasis?
Rapid generation of new skin cells, resulting in an abnormal buildup and thickening of the skin in those areas
What are the different types of psoriasis?
Plaque psoriasis–> Thickened erythematous plaques with silver scales commonly seen on extensor surfaces and scalp. (most common type)
Guttate psoriasis–> Second most common type that commonly occurs in children. Presents with many small raised papules across trunk and limbs.
Pustular psoriasis–> Rare severe form where pastules form under areas of erythematous skin.
Erythrodermic psoriasis–> Rare severe form with extensive erythematous inflamed areas covering most of the skins surface.
What are the specific signs suggestive of psoriasis?
Auspitz sign (small points of bleeding when plaques are scraped off) Koebner phenomenon (development of psoriatic lesions to areas of skin affected by trauma) Residual pigmentation after lesions resolve
How is psoriasis managed?
Topical steroids Topical vitamin D analogues Topical dithranol Topical calcineurin inhibitors Phototherapy It can be difficult to treat and psychosocial support is important
What are the key psoriarisis complications/ associations?
Nail psoriasis
Psoriatic arthritis
Psychosocial implications
Other co-morbidities
What causes arterial ulcers?
Poor blood supple to the skin due to peripheral arterial disease
What causes venous ulcers?
Pooling of blood and waste products in the skin secondary to venous deficiency (varicose veins, DVT e.t.c.)
What causes ulcers?
When small wounds (e.g. tiny cut or pressure sore) cannot heal properly due to poor blood supply. It progressively gets larger and more difficult to heal and can potentially cause complications such as infection.
What distinguidhes an arterial ulcer?
Absent pule Pallor Tend to be smaller More regular border Grey colour (poor blood supply) Less likely to bleed More painful Pain at night when legs elevated Pain worse when elevated
What distinguishes a venous ulcer?
Oedematous flushed skin Hyperpigmentation to skin Varicose eczema Tend to be larger Irregular border More likely to bleed Pain relieved by elevation and worse on hanging.
What is an ulcer?
Loss of skin below the knee on the leg or foot that takes 2 or more weeks to heal.
How are ulcers managed?
Treat underlying cause (arterial or venous disease)
Good wound care (debridement, cleaning, dressing, antibiotics)
Plastic surgery if severe.
What causes the majority (80%) of ulcers?
Venous pathology
What causes ulcers?
Venous insufficiency Arterial insufficiency Pressure ulcers Diabetic neuropathy. Infection Trauma Vasculitis Malignancy
Where are venous ulcers typically found?
Gaiter region of leg (just above ankle to below knee)
Where are arterial ulcers typically found?
Distally at sites of trauma and in pressure areas (e.g. heel) or higher up the leg.
How can venous/ arterial ulcers be diagnosed?
Clinically
Doppler ultrasound
What are neuropathic ulcers like?
Painless ulcers that form on pressure points on the limb. Typically punched out appearance.
What are the main types of skin cancer?
Basal cell carcinoma
Melanoma
Squamous cell carcinoma
Breast cancer
What is squamous cell carcinoma?
Locally invasive malignant tumour of the squamal keratinocytes (outermost keratinocytesin the epidermis).
How does squamous cell carcinoma typically present?
On sun-exposed sites later in life.
Keratotic ill-defined nodules that may ulcerate and can grow rapidly.
How is squamous cell carcinoma treated?
Surgical excision
Radiotherapy
What is the most common malignant skin cancer?
Basal cell carcinoma
Why does BCC occur?
UV radiation triggers changes in the basal cells in the epidermis, resulting in uncontrolled growth
What can BCC look like?
- Open sore that doesnt heal
- Shiny bump/ nodule
- Reddish patch/ irritated area
- Scar-like area
- Small pink growth with slightly raised, rolled edged and crusted indentation
How is BCC treated?
Surgically excised with wide borders and histology to ensure clear and adequate tumour margins.
Cyrotherapy
Photodynamic therapy
When does SCC occur?
When DNA damage from exposure to UV radiation of other damaging agents trigger abnormal cheanges in the squamous cells of the epidermis.
What does SCC look like?
- Scaly red patches with irregular borders
- Open sore that bleeds or crusts
- Elevated growth with central depression
- Wart- like growth that crusts
Why is melanoma more dangerous than BCC and SCC?
Because of its ability to spread to other organs more rapidly if not treated early. (Most malignant skin cancer)
Why does melanoma occur?
When DNA damage due to UV radiation causes mutations in melanocytes, resulting in uncontrolled cellular growth.
What are the two types of melanin and what is the difference?
Eumelanin and pheomelanin. Only eumelanin attempts to protect the skin by releasing melanin causing it to tan (Darker skinned people have more eumelanin and so are at less risk of melanoma)
What does melanoma look like?
Can present in many different shapes, sizes and coulours. >95% show very dark colour/ black in part of lesion
ABCE symptoms to diagnose melanoma?
Asymmetrical shape Border irregularity Colour irregularity Diameter Elevation/ evolution
What are the different types of melanoma?
- Superficial spreading (most common form that usually arises in a mole)
- Lentigo maligna
- Acral lentiginous (most common in people of colour)
- Nodular melanoma (most aggressive type)
How is melanoma treated?
Surgical excision (only curative in early cases) For metastatic disease--> Removal of regional lymph nodes, isolated limb perfusion, radiotherapy, immunotherapy and chemotherapy.
What is cellulitis?
An infection of the skin and soft tissue underneath
What causes cellulitis?
A breach in the skin barrier allowing a point of entry for bacteria. (e.g. trauma, eczema, fungal nail infection, ulcers)
How does cellulitis present?
Erythema Warm to touch Tense/ thickened Oedematous Bullae (fluid filled blisters) Golden-yellow crust (indicates staph. aureus infection)
What are the most common causes of cellulitis?
Staph. aureus
Group A and Group C Streptococcus
MRSA
How is cellulitis treated?
Flucloxacillin. (antibiotic that is very effective against staph and gram positive infections)
What is necrotising fasciitis?
A rare but serious bacterial infection that affects the fascia (sub-cutaneous tissue)
What does necrotising fasciitis cause?
Bacteria release toxins that cause necrosis of the fascia, fat and eventually skin
What are the main symptoms of necrotising fasciitis?
Intense pain that is out of proportion to skin damage
Flu-like symptoms (fever)
Small but painful cut/ scratch
May develop swelling and redness, diarrhoea/ vomiting, dark blotches.
How is necrotising fasciitis treated?
Surgery to remove infected tissue
Antibiotics
Supportive treatment
What is the outlook for necrotising fasciitis?
1-2 in every 5 cases is fatal.
Can progress very quickly
What causes necrotising fasciitis?
When bacteria get into deep tissue, either through the bloodstream or an injury or wound.
