Dermatology Flashcards
What is basal cell carcinoma?
Skin neoplasm
AKA rodent ulcer
Summarise the epidemiology of basal cell carcinoma
Commonest form of skin malignancy Common in those with fair skin Common in areas of high sunlight exposure Common in elderly Rare before age of 40 Lifetime risk in Caucasians = 1 in 3
Explain the aetiology of basal cell carcinoma
Prolonged sun exposure/UV radiation
What are the risk factors for basal cell carcinoma?
Prolonged sun exposure/UV radiation Fair skin Gorlin's syndrome - hedgehog IC signalling cascade Arsenic - contaminated well water Xeroderma pigmentosum Transplant patients
What are the presenting symptoms of basal cell carcinoma?
A chronic slowly progressive skin lesion
Usually on face, scalp, ears, trunk
What are the signs O/E of basal cell carcinoma?
Nodulo-ulcerative (most common):
Small gistening translucent skin over coloured papule, visible telangectasia, raised pearly edges
Morphoeic: yellow/white waxy plaque w ill-defined edge, more aggressive
Superficial: multiple pink/brown scaly plaques w fine edge on trunk
Pigmented:
Specks of brown/black pigment may be present in any BCC
How is basal cell carcinoma investigated?
Biopsy rarely necessary
Diagnosis mainly on clinical suspicion
What is erythema multiforme?
An acute hypersensitivity reaction of the skin and mucous membranes
Summarise the epidemiology of erythema multiforme
Any age group
Mainly in children and young adults
Twice as common in males
Explain the aetiology of erythema multiforme
Degeneration of basal epidermal cells
Development of vesicles between cells in basement membrane
Lymphocytic infiltrate around BVs and at dermo-epidermal junction
What are the presenting symptoms of erythema multiforme?
Non-specific prodromal symptoms of URTI
Sudden appearance of itching/burning/painful skin lesions
Skin lesions may fade leaving pigmentation
What are the signs O/E of erythema multiforme?
Classic target (bull’s eye) lesions w rim of erythema surrounding paler area
Vesicles/bullae
Urticarial plaques
Lesions often symmetrical and distributed over arms and legs, including palms, soles, and extensor surfaces
What are the risk factors for erythema multiforme?
Prior occurrence
Herpes simplex virus infection
Mycoplasma pneumonia
How is erythema multiforme investigated?
- Bloods
FBC - abnormal WCC
U+Es - elevated urea, nitrogen/creatinine due to volume depletion - HSV serology
+ve for HSV-1 or 2 IgM if HSV infection - Rapid PCR
+ve for varicella DNA - Cold-haemagglutination serology
+ve if M pneumoniae infection - CXR:
bronchial thickening
interstitial infiltration
Subsegmetnal atelectasis of lower lobe
What is erythema nodosum?
Panniculitis (inflammation of subcutaneous fat tissue) presenting as red or violet subcutaneous nodules
Summarise the epidemiology of erythema nodosum
Usually affects young adults
3x more common in females
Explain the aetiology of erythema nodosum
Delayed hypersensitivity reaction to antigens associated with various infectious agents, drugs and diseases
Commonly SARCOIDOSIS, drugs (sulphonamides, OCP, dapsone, penicillin) + streptococcal infection
How does erythema nodosum present?
Tender red/violet nodules on both shins Sarcoidosis - uveitis, red eyes, retinal nodules, candle-wax drippings Joint pain Fever Signs of underlying cause
How is erythema nodosum investigated?
Determine underlying cause
- FBC - raised WCC
- Anti-streptolysin-O titre - raised in Strep infection
- ESR - raised
- CXR - bilateral hilar adenopathy in sarcoidosis, unilateral in TB, histoplasmosis etc
- PPD skin testing - +ve in TB
What are the risk factors for erythema nodosum?
Streptococcal infection Sarcoidosis Tuberculosis Coccidiodomycosis Histoplasmosis Blastmycosis Behcet's disease OCPs Leprosy
What is a lipoma?
Slow-growing, benign adipose tumours that are most often found in the subcutaneous tissues
Summarise the epidemiology of lipomas?
Seen at any age
More common between 40-60 years
Relatively common
Explain the aetiology of lipomas
Benign tumours of adipocytes
What are the risk factors for lipomas?
Genetic predisposition - familial multiple lipomatosis, Gardner’s syndrome
How do lipomas present?
Anywhere, often upper arms <5cm Lobulated Non-tender, painless Slowly enlarging Soft, compressible, mobile Do not fluctuate or transilluminate Normal overlying skin Local LN not palpable
Only painful on nerve compression/fat necrosis due to trauma
How is a lipoma investigated?
Clinical diagnosis usually
US/MRI/CT used if in doubt
What is molluscum contagiosum?
A common skin infection caused by a pox virus that affects children and adults
Summarise the epidemiology of molluscum contagiosum
Common
90% of patients < 15 years
Explain the aetiology of molluscum contagiosum
Viral skin infection caused by molluscum contagiosum virus (MCV)
Type of pox virus
Transmission by direct skin contact
What are the risk factors for molluscum contagiosum?
Close contact with infected individual - towels, sex, clothes
Kids
Immunodeficient - HIV
Swimming
What are the presenting symptoms of molluscum contagiosum?
Incubation period: 2-8 weeks
Usually asymptomatic
Tenderness, pruritus and eczema around lesion
Lesions last for around 8 months
What are the signs O/E of molluscum contagiosum?
Firm, smooth, umbilicated papules
2-5mm in diameter
Children - trunk, extremities
Adults - lower abdo, genital area, inner thighs (sexual contact)
How is molluscum contagiosum investigated?
Clinical diagnosis
Dermatoscopy if doubt
What are pressure sores?
Damage to the skin, usually over a bony prominence, as a result of pressure
Summarise the epidemiology of pressure sores
Very common in hospitals
Most commonly occurs in elderly
Explain the aetiology of pressure sores
Constant pressure limits blood flow to the skin leading to tissure damage
Occur as a result of pressure, friction and shear
What are the risk factors for pressure sores?
Immobility
Alzheimer’s disease
Diabetes
What are the presenting symptoms and signs of pressure sores?
Occur over bony prominence - sacrum, heel
Very tender
If infected - fever, erythema, foul smell
How are pressure sores investigated?
No investigations necessary
Clinical diagnosis
What score is used to predict risk of pressure sores in patients?
Waterlow Score
What is psoriasis?
Chronic inflammatory skin disease, which has characteristic lesions and may be complicated by arthritis
Summarise the epidemiology of psoriasis
1-2% of population
Peak age of onset = 20 years
Explain the aetiology of psoriasis
Unknown
Genetic, environmental factors and drugs implicated
What are the risk factors for psoriasis?
Genes - IL23R, IL12B, TNF-a
Strep throat - guttate psoriasis
Flares - viral infection, immunisations
Local trauma - trauma/injection/scar (Koebner phenomenon)
What are the presenting symptoms of psoriasis?
Itching and occasionally tender skin
Pinpoint bleeding with removing scales (Auspitz phenomenon)
What are the signs O/E of psoriasis?
Discoid/nummular - symmetrical, well-demarcated erythematous plaques w silvery scales over extensor surfaces (knee, elbow, scalp, sacrum)
Flexural - less scaly plaques in axilla, groins, perianal and genital skin
Guttate - small, drop-like lesions on trunk and limbs
Palmoplantar - erythematous plaques w pustules on palms and soles
Generalised pustular - pustules over limbs and torso
Joint signs
How is psoriasis investigated?
Most patients don’t need investigations
Guttate - anti-streptolysin-O titre, throat swab
Flexural - skin swabs to exclude candidiasis
Nail clipping analysis for onychomycosis (fungal infection)
Joint involvement analysed by checking for RF and radiographs
What is urticaria?
Itchy, red, blotchy rash resulting from swelling of the superficial part of the skin
AKA hives
Summarise the epidemiology of urticaria
15% get at some point
Acute > chronic
Explain the aetiology of urticaria
Mast cell activation in the skin, resulting in histamine release
Cytokine release –> capillary leakage –> skin swelling and vasodilation –> erythematous appearance
What are the possible triggers for urticaria?
Acute:
- Allergies (foods, bites, stings)
- Viral infections
- Skin contact with chemicals
- Physical stimuli
Chronic:
- Chronic spontaneous urticaria - meds, stress, infections
- Autoimmune
What are the presenting symptoms of urticaria?
Central itchy white papule or plaque surrounded by erythematous flare
Lesions vary in size and shape
May be associated w swelling of soft tissues of eyelids, lips and tongue (angiooedema)
Individual lesions usually transient
How do the timescales of acute and chronic urticaria differ?
Acute - symptoms develop quickly but normally resolve within 48h
Chronic - rash persists for > 6 weeks
How is urticaria investigated?
Usually clinical
Tests may be required for chronic - FBC, ESR/CRP, patch testing, IgE tests
What is eczema?
An inflammatory skin condition characterised by dry, pruritic skin with a chronic relapsing course
Summarise the epidemiology of eczema
All age groups
Most commonly diagnosed before 5 years of age
Childhood prevalence = 10-20%
Explain the aetiology of eczema
Genes + environment
Defects in barrier function + immune dysregulation following allergen exposure
Common loss-of-function variants of epidermal barrier protein FILAGGRIN = major predisposing factor –> leads to lower levels of natural moisturising factor in stratum corneum
Skin also deficient in extra-cellular lipids including ceramides
Breaks in epidermal barrier allow increased exposure and sensitisation to antigens
What are the presenting symptoms of eczema?
Itchy, dry skin Heat Tenderness Redness Weeping Crusting
What are the signs O/E of eczema?
Acute: Poorly demarcated erythematous oedematous dry scaling plaques Papules Vesicles w exudation and crusting Excoriation marks
Chronic: Thickened epidermis Skin lichenification Fissures Change in pigmentation
Where does atopic eczema mainly affect?
Face and flexures
What is sebhorrheic dermatitis?
Appears where there are lots of sebaceous glands - upper back, nose and scalp
Not a result of allergy (like other types of eczema)
Any age
Yellow greasy scales on erythematous plaques
Greasy, swollen skin
Where is seborrhoeic dermatitis mainly affect?
Eyebrows Scalp Presternal area Upper back Nose
What are the risk factors for eczema?
Age < 5 FHx Allergic rhinitis Asthma Anthelmintic treatment in utero
What is atopic dermatitis?
Type of eczema
Chronic and inflammatory
Exact cause unknown - happens when immune system goes into overdrive in response to exo/endogenous allergen
Usually begins in childhood (first 6 months)
Dry, scaly skin Erythema Itching Cracks behind ears Rash on cheeks, arms, and legs Open, crusted or weepy sores
What is contact dermatitis?
Happens when skin touches irritating substances or allergens
These make skin inflamed, causing it to burn, itch and become red
Usually on hands
Most common irritants: solvents, industrial chemicals, detergents, fumes, tobacco smoke, paints, bleach, wool, acidic foods, astringents, alcohol in skin products
Redness and rash
Burning or swelling
Blisters that weep or crust over
What is dyshidrotic eczema?
A condition that produces small, itchy blisters on edges of the fingers, toes, palms and soles of the feet
Triggers = stress, allergies (hayfever), moist hands and feet, or exposure to nickel, cobalt, or chromium salts
2x in women
Small fluid-filled blisters (vesicles) Itching Redness Flaking Scaly, cracked skin Pain
What is discoid eczema?
AKA nummular
Common type of eczema that can occur at any age
Symptoms = Round, coin-shaped spots Itching Dry, scaly skin Wet, open sores
Triggers = insect bites, reactions to skin inflammation, dry skin in winter
What is eczema herpeticum?
Rare but serious complication, which can happen when skin affected by eczema comes into contact with herpes virus
Most often caused by contact w cold sore (HSV-1)
Usually occurs on head, neck, or trunk
Rash that causes blisters
Malaise, swollen LNs, fever, chills, fatigue
Medical EMERGENCY
How is eczema investigated?
Usually clinical diagnosis
Contact dermatitis - skin patch allergy testing
Atopic eczema - lab testing, eg elevated IgE levels
Skin biopsy - exclude mycosis fungoides
What are epidermoid and pilar cysts?
Used to be known as sebaceous cysts
But contain KERATIN, not sebum, and neither originates from sebaceous glands
Epidermoid cysts originate from epidermis
Pilar cysts from hair follices
Cyst = closed sac with a lining (epidermis or hair root cells) + contents that are liquid or semi-solid (keratin)
Summarise the epidemiology of epidermoid and pilar cysts
Epidermoid - young and middle-aged adults
Pilar - women more than men, middle-aged
Explain the aetiology of epidermoid and pilar cysts
High tesosterone and use of androgenic anabolic steroids
Epidermoid - Gardner’s syndrome / implantation of epidermis into dermis during trauma, surgery / blocked pore next to piercing / nevoid BCC syndrome on head and neck
Pilar - inflamed hair follicle
What are the risk factors for epidermoid and pilar cysts?
Acne
FHx - pilar (autosomal dominant)
Gardner’s syndrome
What are the presenting symptoms of epidermoid and pilar cysts?
Grow slowly Some become infected (red and sore) Cheesy foul-smelling pus discharge Often multiple Common in hair-bearing regions
What are the signs O/E of epidermoid and pilar cysts?
Round, smooth, tethered lump just under skin surface
Overlying skin punctum
May discharge granular creamy foul-smelling material
Pilar = scalp Epidermoid = face, neck, genital skin, upper trunk
How are epidermoid and pilar cysts investigated?
Clinical diagnosis
None needed
Skin biopsy/FNA to rule out differentials
What is squamous cell carcinoma?
Malignancy of epidermal keratinocytes of the skin
Summarise the epidemiology of squamous cell carcinoma
2nd most common cutaneous malignancy - 20% of all skin cancers
Middle-aged and elderly
Light-skinned at higher risk
2-3x more common in males
Explain the aetiology of squamous cell carcinoma
UV radiation
Sun exposure can lead to actinic keratosis (sun-induced precancerous lesion)
What are the risk factors for squamous cell carcinoma?
UV radiation
Radiation
Carcinogens (eg tar derivatives, cigarette smoke)
Chronic skin disease (eg SLE)
HPV
Long-term immunosuppression
Defects in DNA repair (eg xeroderma pigmentosum)
What are the presenting symptoms of squamous cell carcinoma?
Skin lesion
Ulcerated
Recurrent bleeding
Non-healing
What are the signs O/E of squamous cell carcinoma?
Variable appearance - may be ulcerated, hyperkeratotic, crusted or scaly, non-healing
Often on sun-exposed areas
Palpate for local lymphadenopathy
How is squamous cell carcinoma investigated?
Skin biopsy - confirm malignancy and type
FNA/LN biopsy - if metastasis suspected
Staging - using CT, MRI, PET
What is herpes simplex infection?
Infection with HSV-1 or HSV-2 causing oral, genital, and ocular ulcers
Explain the aetiology of herpes simplex infection
HSV-1 –> herpes labialis (cold sores)
But also causes 50% of initial episodes of genital herpes
Also associated w HSV encephalitis
HSV-2 –> genital herpes
Large, enveloped dsDNA viruses
Latent and lytic state
Lytic infection = viral replication + transport of virus to skin, infects skin and mucosal surfaces
What are the presenting symptoms of herpes simplex infection?
Dysuria (in women)
Tingling prodrome
Genital/oral painful ulcer
What are the signs O/E of herpes simplex infection?
Lymphadenopathy (rare in oral)
Genital ulcer - multiple, painful ulcers start as vesicular lesions –> ulceration –> crusted lesions
Oral ulcer - single, recurrent, painful, self-limited ulcer along vermilion border
How is herpes simplex infection investigated?
Viral culture: +ve
HSV PCR: +ve
Type-specific serological IgG assay: +ve antibody to HSV-1 or HSV-2
What is melanoma?
Malignancy arising from neoplastic transformation of melanocytes, the pigment-forming skin cells
Summarise the epidemiology of melanoma
Leading cause of death from skin disease
Steadily increasing incidence
White races have 20x increased risk
Explain the aetiology of melanoma
DNA damage caused by UV radiation leads to neoplastic transformation
50% arise in existing naevi
50% arise in previously normal skin
What are the 4 histopathological types of melanoma
Superficial spreading (70%):
- arises in pre-existing naevus
- expands in radial fashion before vertical growth phase
Nodular (15%):
- arises de novo
- aggressive
- no radial growth phase
Lentigo maligna (10%):
- more common in elderly w sun damage
- large flat lesions
- progresses slowly
- usually on face
Acral lentiginous (5%):
- palms, soles, subungual areas
- most common type in non-white populations
What are the presenting symptoms of melanoma?
Change in size, shape, or colour of a pigmented skin lesion Redness Bleeding Crusting Ulceration
What are the signs O/E of melanoma?
ABCDE for examining moles: Asymmetrical Borders uneven Two or more colours Diameter > 6mm Evolving size, shape, colour
How can melanoma be investigated?
Excisional biopsy - histological diagnosis and determination of Clark’s Levels and Breslow Thickness (both determine depth of penetration of melanoma)
Lymphoscintigraphy - radioactive compound injected into lesion and images taken over 30m to trace lymph draining - identify sentinel nodes
Sentinel LN biopsy - check for metastatic involvement
Staging - US, CT, MRI, CXR
Bloods - LFTs (common site of mets)
What are the risk factors for melanoma?
FHx of melanoma Personal Hx of melanoma/skin cancer Hx of atypical naevi Pale skin Red or blonde hair Sun exposure/sun bed use Immunosuppression Xeroderma pigmentosum
What are the nail signs in psoriasis?
Pitting
Onycholysis
Subungual hyperkeratosis
