Dermatology Flashcards
Steven Johnson syndrome
Mucocutaneous necrosis at 2 or > sites
Vague URTI sx start 2-3wks after drug, + 2 days before rash that affects <10% of body
- Painful erythematous macule evolving to form target lesions
- Severe mucosal ulceration of 2 or > surfaces e.g. conjunctiva, oral cavity, labia, urethra
- Necrosis distinguishes from erythema multiforme
- Skin may be limited or extensive involvement
Erythema multiforme
Hypersensitivity triggered mainly by HSV
- Erythematous well-defined round lesions appear on extensor surfaces
- Minimal mucosal involvement
No tx usually needed but can tx cause e.g. acyclovir
Toxic epidermal necrosis
Usually drug-induced
- Flu like sx may precede skin involvement which affects >30% body surface
- Extensive skin + mucosal necrosis accompanied by systemic toxicity
- Widespread painful dusky erythema then necrosis of large sheets of epidermis
Rash seen in acute meningococcaemia
Non-blanching purpuric rash on trunk + extremities which may be preceded by a blanching maculopapular rash + can rapidly progress to ecchymoses, haemorrhage bullae + tissue necrosis
Erythroderma
Exfoliative dermatitis involving >90% of skin surface
- Skin appears inflamed, oedematous + scaly
- Systemically unwell
Tx underlying cause, emollients + wet wraps, topical steroids, treat 2 infection/fluid loss/ electrolyte imbalance/hypothermia/capillary leak syndrome
Causes of erythroderma
Previous skin disease
- Eczema
- Psoriasis
Drugs - sulphonamides, gold, sulfonylureas, penicillin, allopurinol
Dermatological emergencies
- Erythema multiforme
- Erythema nodosum
- SJS
- TEN
- Meningococcal septicaemia
- Eczema herpeticum
- Necrotising fasciitis
Eczema herpeticum
Widespread eruption - serious complication of atopic eczema
Causes = HSV
Extensive crusted papule, blisters + erosions
Systemically unwell
Tx - acyclovir
Necrotising fasciitis
Rapidly spreading infection of the deep fascia with 2. tissue necrosis
Causes = group A haemolytic strep
Presentation of necrotising fasciitis
Severe pain Erythematous, blistering + necrotic skin Systemically unwell Crepitus (subcut emphysema) XR may show soft tissue gas
Cellulitis
Involves the deep subcutaneous tissues
- Spreading bacterial infection of the skin
- Strep pyogenes + staph aureus
Erysipelas
Acute superficial form of cellultis + involves the dermis + upper subcut tissue
- Distinguished from cellulitis by a well-defined, red raised border
Superficial fungal infections causes
3 main groups
- Dermatophytes (tinea/ringworm)
- Yeasts e.g. candidiasis
- Moulds e.g. aspergillus
Tinea incognito
Inappropriate tx of tinea infection with topical or systemic corticosteroids - ill defined + less scaly + spreads more
- Take skin scrapings, hair or nail clippings for correct diagnosis
What is BCC?
Slow growing, locally invasive malignant tumour of epidermal keratinocytes
- Most common malignant skin tumour
Appearance of BCC
Various morphological types - nodular (most common), superficial (plaque like), cystic, morphoeic (sclerosing), keratitis + pigmented
Nodular - small, skin-coloured papule or nodule with surface telangiectasia + a pearly rolled edge. Lesion may have a necrotic or ulcerated centre (rodent ulcer)
Most common over head + neck
SCC
Locally invasive malignant tumour of epidermal keratinocytes which can metastasise
Keratotic (scaly, crusty) ill-defined nodule which may ulcerate
What is malignant melanoma?
Invasive malignant tumour of epidermal melanocytes which has the potential to metastasise
More common on legs in W, trunk in M
Causes of melanoma
UV exposure
Skin type I (always burns, never tans)
Hx of multiple moles/atypical moles
Fam hx/previous hx
ABCDE symptoms
*major suspicious features
Asymmetrical shape* Border irregularity Colour irregularity* Diameter >6mm Evolution of lesion (e.g. change in size and/or shape)* Symptoms e.g. bleeding, itching
Types of melanoma
- Superficial spreading (lower limbs in middle/young aged, related to intermittent high-intensity UV exposure)
- Nodular melanoma (common on trunk in young/middle aged, related to intermittent high-intensity UV exposure)
- Lentigo maligna melanoma - common on face, in elderly. Related to long-term cumulative UV exposure
- Acral lentiginous (common on palms, soles + nail beds in elderly with no clear relation to UV exposure)
Hidradenitis suppurativa
Chronic, painful, inflammatory skin disorder.
Characterized by development of inflammatory nodules, pustules, sinus tracts, and scars in intertriginous areas. Obstructs apocrine glands + prevents keratinocytes properly shedding
Suspect in pubertal or post-pubertal patients who have a diagnosis of recurrent furuncles or boils, especially in intertriginous areas.
Women > men
Adults under 40.
Lichen planus
Unknown aetiology, probably immune mediated
itchy, papular rash on the palms, soles, genitalia and flexor surfaces of arms
Rash often polygonal in shape, with a ‘white-lines’ pattern on the surface (Wickham’s striae)
Koebner phenomenon may be seen (new skin lesions appearing at the site of trauma)
Oral involvement in 50%: white-lace pattern on the buccal mucosa
Seborrhoeic Dermatitis
Seborrhoeic dermatitis in adults is a chronic dermatitis thought to be caused by an inflammatory reaction related to a proliferation of a normal skin inhabitant, a fungus called Malassezia furfur
Eczematous lesions on the sebum-rich areas: scalp (may cause dandruff), periorbital, auricular and nasolabial folds
otitis externa and blepharitis may develop
Tx:
- Scalp = 1st line = zinc prytithione (head + shoulders) and tar (neutragena t gel). 2nd line = ketaconazole
- Face + body. 1st line = ketaconazole
Pityriasis rosea
Presents with a salmon coloured solitary patch ‘herald patch’ which enlarges over a few days followed by generalised bilateral and symmetric macules with collarette scale. Pruritus is sometimes present. It self resolves within 6 – 8 week
- Christmas tree distribution
Pathogenesis of vitiligo?
Autoimmune destruction of melanocytes
Malignant melanoma - acral lentiginous
Arises in dark skinned individuals on their palms or soles. It is not linked to UVB induced DNA damage unlike the other types
What condition is described as ‘stuck on’?
Seborrheic keratosis
What is the best prognostic factor in melanoma?
Breslow thickness
Leser-trelat sign
Sudden appearance of multiple seborrheic keratosis and is an indicator of a gastrointestinal tract carcinoma
Pathology of pemphigus vulgaris
IgG antibody against desmoglein
Desmosomes are located in the stratum spinosum between keratinocytes. Antibodies against the desmoglein component result in painful flaccid bullae or blisters that rupture easily on both skin and oral mucosa. It is treated with corticosteroids.
Lichen plans 6 ‘p’s
Pruritic, purple, polygonal, planar papules and plaques
It also often occurs with reticular white lines on the mucosal surfaces (Wickham striae). There is an association with hepatitis C.
