Dermatology Flashcards
Name 5 functions of the skin
- Barrier to infection
- Thermoregulation
- Protection against trauma
- Protection against UV
- Vitamin D synthesis
- Regulate H2O loss
What is the pH of normal skin?
5.5 = allows protease to remain on the skin
Describe skin pathophysiology
New cells in basal layer of epidermis vs mature corneocytes shed from surface of stratum corneum (desquamation)
How does desquamation work?
Involves degradation of extracellular corneodesmosomes under the action of protease enzymes
Name the 3 layers of skin
- Epidermis
- Dermis
- Subcutaneous tissue
What are the layers of the epidermis?
- Stratum corneum (outmost - layer of keratin)
- Stratum lucid
- Stratum granulosum
- Stratum spinous
- Stratum basale (dividing cells)
What is the stratum corneum made up of?
Corneodesmosomes = adhesion molecules keeping corneocytes together
Desmosomes
What does the dermis layer of skin contain?
Meissner’s corpuscle - light touch
Pacinian corpuscle = coarse touch and vibration
Name 4 cell types of the epidermis
- Keratinocytes = produce keratin as protective barrier
- Langerhans cells = present antigens and activate T cells
- Melanocytes = produce melanin (protect from UV)
- Merkel cells = contain specialised cells for sensation
Name 3 common causes of an itch WITH rash
- Urticaria
- Atopic eczema
- Psoriasis
- Scabies
Name 3 common causes of an itch WITHOUT a rash
- Renal failure
- Jaundice
- Iron deficiency
- Lymphoma
- Polycythaemia
- Pregnancy
What does an increase in corneodesmosomes lead to?
Thickening of skin = psoriasis
What does a decrease in corneodesmosomes lead to?
Thinning of skin = eczema
What is main cause of all skin cancer?
Sun exposure - UV light
Name 3 types of skin cancer
- Basal Cell Carcinoma (75%) = benign, grows slowly
- Squamous Cell Carcinoma (20%) = can metastasise, grows rapidly
- Melanoma (5%) = most malignant form of skin cancer
Give 4 risk factors for melanoma
- Sunlight exposure
- Red hair
- High density freckles
- Skin type 1
- Atypical moles
- Family history
- Immunosuppression
What is the presentation/ABCDE features of melanoma?
Asymmetry of mole Border irregularity Colour variation Diameter >6mm Elevation/evolution
Name 4 type of melanoma
- Lentigo malignant melanoma
- Superficial Spreading malignant melanoma
- Nodule malignant melanoma
- Acral lentiginous malignant melanoma
Describe the progression from melanocytic nave (mole) to nodular melanoma
Melanocytic nave –> dysplastic melanocytic nave –> in situ melanoma –> superficial spreading melanoma –> nodular melanoma
What is a lentigo malignant melanoma?
A patch of lentigo maligna - a slow growing macular area of pigmentation often on face in elderly
Develops a nodule signalling invasive malignancy
What is a Superficial Spreading malignant melanoma?
Large, flat, irregularly pigmented lesion
Grows laterally before vertical invasion
What is a Nodule malignant melanoma?
Rapidly growing pigmented nodule which bleeds or ulcerates (most aggressive)
What is a Acral lentiginous malignant melanoma?
Pigmented lesions on the palm, sole or under the nail
What is Hutchinson’s sign?
Pigmentation of nail and proximal nail fold
Important sign of subungual melanoma
Give 3 factors that can be used to determine the prognosis of melanoma
- Breslow’s thickness - the thinner (<1mm) the better
- Younger = better prognosis
- Female = better prognosis
What is the treatment for melanoma?
Wide surgical excision
What is Glasgow’s 7 point checklist?
Criteria for melanomas Major criteria 1. Change in size 2. Change in shape 3. Change in colour Minor criteria 4. Diameter >6mm 5. Inflammation 6. Oozing/bleeding 7. Mild itch/altered sensation
Define squamous cell carcinoma (SCC)
Locally invasive malignant tumour of the squamal keratinocytes
How do SCC present?
Keratotic, ill-defined nodules that ulcerate and grow rapidly
What is Bowen’s disease?
SCC in situ
Isolated scaly red plaques resembling psoriasis
What is keratoacanthoma?
Benign variant of SCC
Fasting growing and dome shaped
What are solar keratinises?
Erythematous silver-scaly papules with red base
What is the treatment for a SCC?
Surgical excision with a minimal margin of 5mm
Radiotherapy to affected nodes
Define Basal cell carcinoma (BCC)
Tumour of basal keratinocytes
How does a BCC present?
95% = non-pigmented
Shiny pearly nodules which may ulcerate
Bleeds following minor trauma and doesn’t heal
What is the treatment for a BCC?
Surgical excision
Alternative = radiotherapy, photodynamic therapy, cryotherapy
Define psoriasis
Chronic, inflammatory skin disease due to hyperproliferation of keratinocytes and inflammatory cell infiltration
When does psoriasis usually present?
2 peaks = 20s and 50s
What environmental factors can cause psoriasis in a genetically susceptible individual?
- Group A Streptococcal infection
- Lithium
- UV light
- Alcohol
- Stress
Describe the pathophysiology of psoriasis
T cell activation –> up-regulation of Th1 types of T cell cytokines –> increase uncontrolled hyper proliferation of keratinocytes in epidermis + increase in epidermal cell turnover rate
Name the different types of psoriasis
- Chronic plaque psoriasis
- Flexural psoriasis
- Guttate psoriasis
- Erythrodermic and pustular psoriasis
How does chronic plaque psoriasis present?
Salmon-pink silvery scaly lesions on extensor surfaces of limbs (knees, elbows) with scalp involvement
How does flexural psoriasis present?
Red glazed, non-scaly plaques in flexures (groin, axillae, submammary)
How does Guttate psoriasis present?
Raindrop psoriasis - explosive eruption of small plaques appear on trunk after strep infection
Mainly children and young adults affected
How does erythrodermic and pustular psoriasis present?
Widespread intense inflammation of skin, with malaise, pyrexia and circulatory problems
Name 4 associated symptoms of psoriasis
- Pitting of nail plate
- Onycholysis (separation of fingernail from nail bed)
- Discolouration of nails
- Subungual hyperkeratosis
- Psoriatic arthritis
Describe the treatment of psoriasis
- Emollients and reassurance
- Vitamin D and A analogues (retinoids) - calcipotriol and tazarotene
- Topical corticosteroids - hydrocortisone, betamethasone
- Phototherapy
- Immunosuppression or biological agents - methotrexate, infliximab
What are emollients used for?
Hydrate the skin and reduce itching
How does hydrocortisone work?
Targets cytoplasmic receptors
Leads to reduction in pro-inflammatory cytokines and an increase in anti-inflammatories
Give 3 potential side effects of corticosteroids
- Skin thinning
- Oral candidaisis
- Acne
- Striae
- Bruising
How does calcipotriol work in the treatment of psoriasis?
Vitamin D analogue
Anti-proliferative and anti-inflammatory effects
How does tazarotene work?
Vitamin A analogue
Modifies gene expression and inhibits cell proliferation
Would you prescribe tazarotene to a pregnant lady?
No = highly teratogenic
Why do transdermal drugs need to lipophilic?
In order to get through the lipid rich stratum corneum
Give 2 essential properties of transdermal drugs
- Lipophilic
2. High affinity for their targets
Give 2 advantages of transdermal drug delivery
- Avoids first pass effect, hardly metabolised
- No pain
- Controlled dosing
Describe the pathophysiology of atopic eczema
Abnormal epithelial barrier function - allows antigenic and irritant agents to penetrate and reach immune cells
Initial activation of Th2 type CD4 cells drive inflammatory process (increase in IgE production)
Name 3 exacerbating factors of atopic eczema
- Strong detergents and chemicals
- House dust mites
- Animal fur
- Diet
How does eczema present?
Itchy, erythematous scaly patches in flexures (elbows, ankles, knees)
Increased dryness of skin
Hypo or hyper pigmentation
Risk of secondary infection due to broken skin
What are 2 signs of chronic eczema?
- Excoriations (stretch marks)
2. Skin thickening (lichenification)
What happens to the serum IgE in eczema?
In 80% = raised
How do you diagnose eczema?
Must have itchy skin condition in past 6 months + 3 or more of
- History of involvement of skin creases
- Personal history of asthma or hay fever
- History of generally dry skin
- Childhood onset
Describe the aetiology of eczema
- Genetic predisposition - loss of function mutation in filaggrin
- Environmental triggers and irritants
Describe the treatment for eczema
- Avoid irritants and allergens
- Use emollients
- Hydrocortisone (1st line) or stronger steroids
- Tacrolimus (2nd line) - topical immunomodulators
- Antibiotics for secondary infections
Briefly describe the natural history of eczema
Sub-clinical skin barrier defect –> sub-clnicial inflammation –> AD phase 1 (non-atopic) –> AD phase 2 (true atopic, extrinsic), high IgE
Define allergic dermatitis
Sensitisation of T lymphocytes over a period of time - itching and dermatitis results upon re-exposure to the antigen
Give 3 causes of contact dermatitis
- Detergents
- Soaps
- Oils
- Solvents
- Type 4 hypersensitivity reaction
How does contact dermatitis present?
Rash with Clear demarcation/odd-shaped area
How can you diagnose contact/allergic dermatitis?
Patch testing = identify the allergen
How can you treat contact dermatitis?
Remove cause
Steroids
Anti-pruritic agents
Where does seborrhoeic dermatitis usually effect?
Scalp and face - thickened, scaly skin
What can trigger seborrhoeic dermatitis?
Yeast infection
What is the treatment for seborrhoeic dermatitis?
- Antifungal treatment
2. Keratolytic agents to reduce thickening
What is cellulitis?
Bacterial infection of the deep subcutaneous tissue of the skin
Give 4 risk factors for cellulitis
- Lymphoedema
- Site of entry - leg ulcer, trauma, tinea pedis
- Venous insufficiency
- Leg oedema
- Obesity
Name 3 causes of cellulitis
- Strep pyogenes (most common)
- Staph aureus
- Community acquired MRSA
Give 4 signs of cellulitis
- Erythema, with poorly marked margins
- Inflammation
- Swelling
- Warmth
- Tenderness
- Low grade fever
What is the differential diagnosis in someone it the signs and symptoms of cellulitis?
DVT
What is the treatment for cellulitis?
Phenoxymethylpenicillin and flucloxacillin (erythromycin if allergic to penicillin)
What is necrotising fasciitis?
Rapidly progressive infection of deep fascia resulting in necrosis of subcutaneous tissue
Give 3 risk factors for necrotising fasciitis
- IVDU
- DM
- Homeless
- Recent surgery
What bacteria can cause necrotising fasciitis?
Type 1 = aerobic and anaerobic bacteria
Type 2 = Group A beta-haemolytic strep (strep pyogenes)
Give 4 signs of necrotising fasciitis
- Intense pain that is out of proportion to the skin findings of initial site of infection
- Spreading erythema and pain
- Crepitus
- Fever
- Multi-organ failure –> death
What is the treatment for necrotising fasciitis?
Surgical debridement +/- amputation
Type 1 = broad spec Abx with inclusion of metronidazole
Type 2 = benzylpenicillin and clindamycin
Briefly describe the pathophysiology of acne
Seborrhea (increased sebum production) –> narrowed follicle (due to hypercornification) blocks sebum –> sebum stagnates and p. acne colonises –> irritation, inflammation and attraction of neutrophils
Describe the signs of acne
- Open comedones (blackheads)
- Closed comedones (whiteheads)
- Papules and pustules
- Hyperpigmentation
- Scarring
Describe the treatment for acne
Regular washing with acne soap to remove grease
Benzoyl peroxide (keratolytic) and clindamycin
Topical retinoids - tazarotene
Low dose Abx - doxycycline or minocycline
Hormonal treatment - co-cyprindiol
Give 3 signs of rosacea
- Flushing
- Erythema
- Papules and pustules
How does Rosacea differ for acne?
Rosacea = no comedones and tends to affect older people
Define ulcer
Abnormal breaks in an epithelial surface
Define venous ulceration
Loss of skin below the knee on the leg or foot that takes more than 2 weeks to heal
Give 3 causes of venous ulceration
Sustained venous Hypertension in superficial veins due to:
- Incompetent valves
- Previous DVT
- Atherosclerosis
- Vasculitis - SLE, RA
Describe the pathophysiology of a venous ulcer
Increased pressure –> extravasation of fibrinogen through capillary wall –> perivascular fibrin deposition –> poor oxygenation of surrounding skin
How does a venous ulcer present?
Sloping, gradual edges Large, shallow, irregular and exudative ulcer Oedema of lower leg Venous eczema Varicose veins Lipodermaosclerosis
What investigations would you do on a patient you suspect to have a venous ulcer?
Doppler US - to exclude artery disease
What is the treatment for venous ulceration?
High compression bandaging and leg elevation
What is an arterial ulcer?
Punched out, painful ulcer higher up on the leg or on the feet
What are 3 risk factors for an arterial ulcer?
- Claudication
- Hypertension
- Angina
- Smoking
What are the signs of an arterial ulcer?
- Cold and pale leg
- Loss of leg hair
3 Absent peripheral pulses
How would you confirm an arterial ulcer?
Doppler US
What is the treatment for an arterial ulcer?
Clean and cover
Analgesia
Vascular reconstruction if needed
NO compression bandaging
How do neuropathic ulcers usually present?
Painless
Seen over pressure areas of feet or heel due to repeated trauma
What diseases are associate with neuropathic ulcers?
- DM
2. Neurological disease
How do you treat neuropathic ulcers?
Keep clean and remove pressure/trauma
Correctly fitting shoes
What is the most common cutaneous vasculitis?
Leucocytoclastic vasculitis/angitis
= symmetrical palpable purpura
Give 3 causes of Leucocytoclastic vasculitis
- Idiopathic
- Drugs
- Infection
- Inflammatory disease
- Malignant disease
How do you confirm cutaneous vasculitis?
Skin biopsy
What is the treatment for cutaneous vasculitis?
Analgesia
Support stockings
Dapsone (Abx) or prednisone
Name 3 other types of ulcer
- Infective - TB, syphilis
- Traumatic
- Malignant
- Lymphoedema
- Pyoderma gangranosum
- Drug induced
