Dermatology Flashcards
Define psoriasis
A chronic autoimmune inflammatory skin condition characterised by hyperproliferation of keratinocytes causing scaly, erythematous, circumscribed papules with a silver scale
Summarise the aetiology of psoriasis and the risk factors of psoriasis
Aetiology is unknown
Genetic component - FHx
Precipitating factors: Stress Smoking Infection Alcohol Skin injury Medication
Guttate psoriasis - streptococcal sore throat
Palmar-plantar psoriasis - smoking, middle-aged women, autoimmune thyroid disease
Generalised pustular psoriasis - hypoparathyroidism
Summarise the epidemiology of psoriasis
Mean age of onset 28 years old
Equal in men and women
Affects 1-2% of the population
What are the presenting symptoms of psoriasis?
AUSPITZ SIGN - Pinpoint bleeding with removing scales
Skin lesions may develop at sites of trauma/scars (Koebner phenomenon)
Plaque psoriasis (most common type): Itchy Well circumscribed purple/red/salmon flattened areas of elevation White/silver scales Found on scalp and extensors Dry flaky skin Painful
Guttate psoriasis:
Itchy, red small raindrop plaques on back
Following strep throat infection
Pustular planto-palmar:
Small fluid filled pustules on hands and feet
Flexural:
Red, shiny itchy rash found in skin folds (axilla, groin, perianal, under breast
Erythrodermic:
Systemic body redness and inflammation
Painful and itchy
What are the signs on physical examination of psoriasis?
Nail signs:
Oncholysis (nail falling off nail bed)
Pitting
Subungal hyperkeratosis - scaling under nail
Signs of psoriatic arthritis: Asymmetrical oligoarthritis Symmetrical polyarthritis Distal interphalangeal joint predominance Arthritis mutilans Psoriatic spondylitis
Plaque psoriasis - symmetrical, well-demarcated erythematous plaques with silvery scales over extensor surfaces (knee, elbows, scalp, sacrum)
Flexural psoriasis - red, shiny, less scaly plaques in axilla, groins, perianal and genital skin
Guttate psoriasis - small drop-like lesions over trunk and limbs
Palmoplantar psoriasis - erythematous plaques with pustules on palms and soles
What are the appropriate investigations for psoriasis?
Usually a clinical diagnosis which requires no investigations
Skin biopsy can confirm diagnosis
Guttate psoriasis: anti-streptolysin-O titre, throat swab
Flexural psoriasis: skin swabs to exclude candidiasis
Nail clipping analysis for onychomycosis (fungal infection)
Joint involvement analysed by checking for rheumatoid factor and radiographs
Define herpes simplex virus
Herpes simplex virus is a enveloped, double stranded DNA virus
Infection with HSV-1 or HSV-2 can cause oral, genital, and ocular ulcers. The primary episode occurs during initial infection with HSV, in which the host lacks an antibody response.
HSV-1: mainly oral herpes herpes
HSV-2: mainly genital herpes
HHV-3: varicella-zoster virus - chickenpox and shingles
Summarise the aetiology of herpes simplex virus
HSV1 causes herpes labialis (cold sores)
HSV2 causes genital herpes
HSV are large, enveloped, double stranded DNA viruses
HSV-1 and HSV-2 are acquired at mucosal surfaces or at breaks in the skin. The virus replicates in the epidermis, then infects sensory or autonomic nerve endings and travels by retrograde axonal transport to sensory ganglia.
In the latent phase HSV lives in trigeminal ganglia (face sensory neuron cell bodies) and sacral ganglia (genital sensory neuron cell bodies)
Periodic reactivation of the virus produces lytic replication when the virus travels by anterograde transport down axons to the mucosal or cutaneous surface
Reactivation triggers:
Stress
Skin damage
Viral infection
Summarise the epidemiology of herpes simplex virus
Infection most commonly acquired during childhood
Seropositivty increases with age
Prevalence of HSV1 and HSV2 higher among women
Very common
What are the presenting symptoms of herpes simplex virus
Herpes labialis - cold sores Painful sores in the genital area Itchiness Dysuria Vaginal discharge Fever Headache Flu like prodrome for HSV2 Gingivostomatitis - dry crusting sore of mouth Sore throat
Keratoconjuncitivitis: Red, painful inflammed eye Sensitivity to light Tearing Blurring of vision Herpetic whitlow - rash on fingertip Tingling sensation
Immunocompromised patients may have more severe, prolonged ulceration of the genital or oral mucosa than immunocompetent patients.
What are the signs on physical examination of herpes simplex virus?
Fever Pharyngitis Lymphadenopathy Bilateral tender inguinal lymphadenopathy Multiple tender 1-2 cm erythematous ulcerations Oedematous cervix Pustules Clear discharge
What are the appropriate investigations for herpes simplex virus?
Mainly clinical diagnosis based on appearance of blisters
Viral culture - detect HSV
HSV PCR - positive
Type-specific serological IgG assay: positive antibody to HSV1 or HSV2
Define lipoma
A slow growing, benign tumour composed of adipose tissue, usually found in the subcutaneous tissues particularly of the trunk and proximal limbs. They form well-circumscribed, lobulated lesions composed of adipocytes which are demarcated from surrounding fat by a thin, fibrous capsule
Summarise the aetiology of lipoma
Mostly idiopathic
Hereditary:
Familial multiple lipomatosis
Gardner’s syndrome
Madelung’s disease - benign symmetric lipomatosis on head, neck, shoulders - MEN WITH HEAVY ALCOHOL CONSUMPTION
Dercum’s disease - painful lipomas on trunk, shoulders, arms and legs - MIDDLE AGED WOMEN
MEN 1
Summarise the epidemiology of lipoma
1% of population
Occur at any age
Most common between 40-60 years old
What are the signs and symptoms of lipoma?
SOFT, MOBILE, SUPERFICIAL MASS Usually painless Cutaneous mass <5cm diameter Well circumscribed lesion Separated from surrounding fat by thin, fibrous capsule Skin coloured Smooth normal surface Soft/doughy feeling Fluctuant NOT transilluminate
GI obstruction or bleeding if lipoma found in GI tract
What are the appropriate investigations for lipoma?
Mainly a clinical diagnosis
Can use CT/MRI/USS if doubt about diagnosis - show discrete, encapsulated, homogeneous mass with similar density to normal fat
Biopsy - histology consistent with lipoma
Define erythema nodosum
A common type IV hypersensitivity reaction leading to inflammation of subcutaneous fat, resulting in raised tender purple nodules often over the shins.
Summarise the aetiology of erythema nodosum
25% of cases have no identifiable cause
Infection: Strep pyogenes (MOST COMMON CAUSE) Tuberculosis HIV Chlamydia Leprosy EBV Histoplasmosis
Systemic inflammation:
IBD
Sarcoidosis
Behcets disease
Drugs:
Sulphonamides
Amiodorone
Oral contraceptives
Pregnancy
Malignancies:
Haematological malignancies
Carcinoid tumours
Pancreatic cancer
Summarise the epidemiology of erythema nodosum
Peaks between 20-30 years old
More common in females
Associated with pregnancy
What are the presenting symptoms of erythema nodosum?
Bilateral, tender, red/purple erythematous nodules often on the shins
Lesions appear for 1-2 weeks and leave bruise-like discolouration as they resolve
Lesions do not ulcerate and resolve without atrophy or scarring
May be associated with fever, arthralgia
Fatigue
Anorexia
Weight loss
Symptoms of underlying cause:
GI symptoms (change in bowel habit, blood in stool, abdominal pain) - IBD, Behcets
Cough and SOB - TB
What are the signs on physical examination of erythema nodosum?
Bilateral, poorly defined, red/purple dome-shaped nodules most commonly on the shins
Occasionally appear on the thighs and forearms
Nodules are tender to palpation
Low-grade pyrexia
Joints may be tender and painful on movement
Signs of underlying CAUSE
What are the appropriate investigations for erythema nodosum?
Biopsy if uncertain of diagnosis
Investigations to identify the cause
Bloods:
FBC, ESR, CRP - suggestive of infection (often a leukocytosis)
Serum ACE - raised in sarcoidosis
Anti-streptolysin-O titres - check for streptococcal infection)
m ACE (raised in sarcoidosis)
Throat swab and cultures - check for streptococcous
Mantoux/Head skin testing - for TB
CXR - check for bilateral hilar lymphadenopathy or other evidence of TB, sarcoidosis or fungal infections
If suspect IBD, faecal calprotectin, colonoscopy
Define erythema multiforme
An acute hypersensitivity reaction often due to infections, mainly HSV and mycoplasma, leading to skin and mucosal inflammation. It is characterised by target lesions.
Explain the difference between erythema multiforme minor and major
Erythema multiforme minor NO mucosal involvement
Erythema multiforme major has 2+ mucosal sites involved
Summarise the aetiology of erythema multiforme
Precipitating factor only found 50% of the time
Usually due to a preceding infection Most commonly HERPES SIMPLEX VIRUS and MYCOPLASMA PNEUMONIAE Can also be due to: HIV EBV CMV Hep B Herpes zoster Sulphonamides Penicillins Anticonvulsants
Other precipitating factors:
Inflammatory - e.g. rheumatoid arthritis, SLE, sarcoidosis, ulcerative colitis
Malignancy - e.g. lymphomas, leukaemia, myeloma
Radiotherapy
Summarise the epidemiology of erythema multiforme
Can occur in any age group More common in males Peak incidence in 20s and 30s 20% of cases occur in children Children often have more severe form Recurrent in 30% of patients
What are the presenting symptoms of erythema multiforme?
Prodrome - fever, aches
Rapid onset over 24-48 hours Symmetrical Target lesions - central necrosis surrounded by erythematous rings Tender, itchy, burning rash Lesions start on hands and spread
Lesions may fade and leave pigmentation
Erythema multiforme major:
Painful, itchy, crusting, bleeding ulcerations on mouth
What are the signs on physical examination of erythema multiforme?
Classic target (bull’s eye) lesions with a rim of erythema surrounding a paler area
Vesicles/bullae
Urticarial plaques
Lesions are often symmetrical and distributed over the arms and legs including the palms, soles and extensor surfaces
