Dermatology Flashcards
Describing a skin lesion
• Colour (erythematous, hyperpigmented, hypopigmented)
o Erythema: vasodilation due to inflammation, blanchable
o Purpura: extravasation of blood, non-blanchable
• Site, size, shape
• Morphology: Primary & secondary lesions (refer below)
• Distribution: dermatomal (zoster), flexor (eczema)/ extensor (psoriasis), sun-exposed areas (photosensitivity),
intertriginous, symmetrical / asymmetrical, confluent
• Always check: hair, nail, mucosal membrane, intertriginous areas
Atopic dermatitis
3 hallmark features
• Pruritus
• Ill-defined border
• Epidermal changes
o Acute: erythema, papules, vesicles,
weeping (ruptured vesicles), pomphylx (tiny vesicles in palms and soles)
o Subacute: scaling, crusting
o Chronic: lichenification, hyperkeratosis, fissures
Other clinical features
• Age-specific distribution
• Chronic or relapsing course
• Onset during infancy or early childhood
• Personal / Family history of atopy (atopic dermatitis, asthma, allergic rhinitis)
Management
• Education: avoid rough clothes, pets, hot water, etc
• Emollients
• Oral antihistamine: mainly as sedative
• Topical steroid
• Topical calcineurin inhibitor (tacrolimus)
• Phototherapy
• Systemic immunosuppressants e.g. cyclosporine, azathioprine, MMF, methotrexate
• Biologics: dupilumab (anti-IL4/13), baricitinib (JAK-1)
Primary lesion
Flat lesion:
- macule
- patch
Raised lesion:
- papule
- plaque
- nodule
Fluid
- vesicle-clear fluid (Herpes, chickenpox)
- bulla-clear fluid (Bullous pemphigoid, SJS)
- pustule-purulent (bacterial folliculitis, pustular psoriasis)
- cyst-semisolid (acne)
Purpura
- petechia (platelet disorder)
- ecchymosis (clotting disorder)
Secondary lesion
- crust (impetigo)
- scaling (seborrhoeic dermatitis, psoriasis)
- scar (keloid scar)
- excoriation (atopic dermatitis)
- lichenificaation (atopic dermatitis)
- fissure (dermatitis)
- erosion
- ulcer
- atrophy
- telangiectasia
Ix of dermatology
• Wood’s light: UV 360-365nm for examination of pigmented or depigmented skin lesions
• Punch biopsy: should include epidermis, dermis and subcutaneous fat
• Dermoscope: magnifying glass + polarised light (to reveal deeper structure)
Psoriasis
• Definition: chronic inflammatory skin conditions characterised by a state of hyperproliferation
o Type 1: young-onset, FHx +ve
o Type 2: late onset, associated with metabolic syndrome
Types
• Plaque (MC in adult): common in extensor surface of elbows & knees, scalp, trunk
• Guttate (more common in children): raindrop-like
• Pustular: acute onset of pustules, associated with fever, malaise, etc; precipitated by withdrawal of steroid
• Erythrodermic: generalised erythema & scaling > 75% BSA, precipitated by withdrawal of steroid, infection,
alcohol, stress
• Inverse: on flexor surface
Clinical features
• Well-demarcated (c.f. eczema), erythematous
plaques with silvery scale
• Auspitz sign: removal of scale from plaques causes
pinpoint bleeding
• Koebner phenomenon: development of skin disease in sites
of skin trauma
• Nail dystrophy (90%)
• Psoriatic arthritis (30%)
• Increased risk of CVS disease: chronic inflammatory state
Management
Topical
• Emollient
• Coal tar
• Salicylic acid
• Steroid
• Vit D3 analogue (calcipotriene)
• Calcineurin inhibitor (tacrolimus)
Systemic
• Phototherapy: narrow band UVB
• Acitretin (retinoid derivative)
• Immunosuppressants, e.g. methotrexate,
cyclosporin
• Biologics, e.g. TNFα inhibitors (infliximab),
IL-12/23, IL-17 inhibitors
AVOID systemic steroid - risk of flare-up
Lichen planus
• Definition: acute or chronic inflammation of mucous membranes
or skin
• Clinical features
o 4P: purple, polygonal, pruritic plaques
o Wickham’s striae (fig.): reticulate white-grey lines over surface
• Investigations: skin biopsy, anti-HCV (association)
• Management:
o Topical steroid
o Immunosuppressants, e.g. MTX
Cutaneous lupus erythematosus
Acute cutaneous
lupus (ACLE)
—> 90% systemic
involvement
(ANA +ve,
dsDNA +ve)
- malar rash
- marked photosensitivity
- bullous lupus
Subacute
cutaneous lupus
(SCLE)
- sun-exposed area
Chronic
cutaneous lupus
(CCLE)
—> 90% only
cutaneous
(ANA +ve in
~50% only)
- discoid lupus
Pemphigus vulgaris
- younger onset (40-50)
- intra-epidermal layer
- Pathogenesis: autoantibodies (Anti-desmoglein-1/3) against desmosomes
- S/S: skin+mucosa involvement —> flaccid blisters / erosions that rupture easily
- +ve Nikolsky’s sign: sligh rubbing -> exfoliation of the outermost layer
- Associated with underlying malignancy
- Ix: Skin biopsy for direct IF: IgG/c3 deposits between keratinocytes in chicken wire pattern
Bullous pemphigoid
- older (70), neurological deficit e.g. Parki, stroke
- sub-epidermal layer
- Autoantibodies (Anti-BP180/BP230) against hemi-desmosomes
- S/S: skin only —> pre-bullous Phase (urticaria-like rash) —> bullous phase (tense and firm but does not rupture easily) —> end stage (erosions)
- -ve nikolsky’s sign
- associated with DPP4 inhibitor, frusemide, spironolactone, sulfasalazine, penicillin, penicillamine, b-blockers, immunisation in children
- Ix: skin biopsy —> IgG/c3 deposits along dermal-epidermal junction
Ddx of bullous dermatosis
• Congenital epidermolysis bullosa simplex
• Infectious: SSSS, bullous erysipelas, bullous tinea pedis
• Autoimmune: pemphigus vulgaris, bullous pemphigoid, bullous
SLE, bullous erythema multiforme
• Metabolic: porphyria cutanea tarda
• Drug: drug-induced bullous eruptions
Mx of bullous dematosis
Immediate management:
• Blister care: prick but do NOT de-roof blisters, apply non-adhesive dressings
• Infected: wound swab for culture, give antibiotics
• Immunocompromised: consider HSV/VZV and do viral isolation for culture
Localized bullous pemphigoid:
• Superpotent topical corticosteroids (e.g. clobetasol)
• Oral doxycycline + nicotinamide
Extensive bullous pemphigoid:
• Systemic steroids (dosage depend on severity)
• Steroid sparing agents: e.g. Dapsone, MTX, AZA, MMF, IVIG
Treatment aim for BP: presence of blisters (5-10) once every 1-2 weeks
Herpes zoster
• Clinical features
o Common in >50y —> vaccination
o Dermatomal pain, paresthesia & pruritus for few days, then
o Vesicles in dermatome distribution of sensory
nerves
- Site: trigeminal area, thorax (chest pain)
- Multidermatomal shingles suggest
immunocompromised state
• Complications
o Disseminated infection, Tx IV acyclovir
o Secondary bacterial infection (S aureus)
o Post-herpetic neuralgia: may last > 1y; Tx gabapentin
o Herpetic ophthalmicus [Skin emergencies]
• Management
o Astringent: calamine lotion
o Oral antiviral: acyclovir, famciclovir for 7 days
§ Effective only if started within 48h of onset of rash
o Prevention: herpes zoster vaccine
Tinea infection (ringworm)
• Pathogens: Trichophyton, Epidermophyton, Microsporum
• Clinical features
o Tinea pedis (2 foot 1 hand disease): asymmetrical diffuse scaling of palms & soles - tinea pedis until proven
otherwise
o Tinea manuum (hand), unguium (nail), corporis (body), cruris (groin)
o Tinea incognito: appearance modified by chronic steroid treatment
• Investigations: Wood’s light
• Treatment
o Topical antifungals (e.g. clotrimazole): 1st line
o Oral antifungals (e.g. griseofulvin, itraconazole): if extensive
Scabies
• Pathogen: Sarcoptes scabiei hominis
• Clinical features
o Burrows (pathognomic)
o Excoriated papules / vesicles that mimic eczema: hypersensitivity towards mites
o Common sites of involvements: fingers / toewebs, axilla, groin/genitalia, umbilicus
o Norwegian scabies: plaques above neck (scabies rarely goes up), highly contagious
• Investigations: skin scrapping for microscopy (mite eggs)
• Management
o Permethrin, malathion, ivermectin
o Hot cycle wash & drying for clothing & linen
o Contact tracing
Rash due to viral infections
MP rash
- Measles, rubella
- Enterovirus
- Roseola
- Parvovirus B19
Vesicular rash
- HSV
- VZV
- HFMD (EV71, Coxsackie A16)
Haemorrhagic
- Dengue
- Chikungunya
Hyperplastic
- HPV (warts)
- Poxvirus (molluscum contagiosum)
Centripetal rash
(start on/ predominant on extremities)
• HFMD
• Secondary syphilis
• Dengue
• Rocky mountain spotted fever
Hypersensitivity reactions types and Mx
Overview – types
• Immediate (IgE mediated, type I): isolated urticaria in mild, anaphylaxis in severe
• Delayed (T cell mediated, type IV):
o Mild: itching & maculopapular eruption
o Severe: SCAR (severe cutaneous adverse reaction)
- SJS/ TEN: weeks after drug use
- DRESS (Drug Reaction with Eosinophilia & Systemic Symptoms): weeks after drug use
- AGEP (acute generalised exanthematous pustulosis): 3-4 days after drug use, self-limiting
Overall management
• Anaphylaxis:
o Resuscitation (ABC) – protect airway, give oxygen, fluid resuscitation
o Consult ICU
o IM adrenaline 0.5mg Q5min until signs resolve or S/E (tachycardia, HT, tremor, anxiety)
o Chlorpheniramine IV
o Hydrocortisone IV: reduce but do not eliminate risk of second phase reaction
o Observe at least 24h for second phase reaction
o Take blood x mast cell tryptase immediately, 2h after and 24h after (normal does not exclude anaphylaxis)
• Mild: antihistamine +/- H2RA
• Document allergy
Urticaria
Features
• Itchy pale to pink papules / plaques
• Wheals / Hives
• Dermographism
• Transient: individual lesion last < 24 hours
Pathogenesis: mast cell degranulation —> histamine release
• Immune-mediated or non-immune mediated
• Spontaneous or inducible
Causes of spontaneous urticaria: usually idiopathic
Acute urticaria (<6 weeks)
• Idiopathic (~50%)
• Infection e.g. URTI (~40%)
• Drugs (~10%)
• Food (<1%)
Chronic urticaria (>6 weeks)
• Idiopathic (~50%)
• Autoimmune (Ab against IgE): 40-50%
• Chronic infection (e.g. parasites) <5%
Treatment: Non-sedating antihistamines (1st line)
• Cetirizine 10mg daily / Loratadine 10mg daily
• ± Step up to 4x dose e.g. loratadine 20mg BD
SJS/TEN (Steven Johnson Syndrome / Toxic Edpidermal necrolysis)
A rare, severe, life-threatening mucocutaneous reaction characterized by epidermal necrosis and detachment
• < 10% BSA: SJS
• 10-30% BSA: SJS/TEN overlap
• >30% BSA: TEN
Risk factors: HIV (100x), malignancy (30-60x)
Differential diagnoses
• Erythema multiforme
• Erythroderma
• Pemphigus
• AGEP
• Staphylococcal scalded skin syndrome
• Acute GvHD
• Drugs (>85%): check at least 8 weeks of drug histor y
o Anticonvulsants: carbamazepine (HLA-B1502), phenytoin, phenobarbital, lamotrigine, oxcarbazepine
- Note cross-reactivity between aromatic anticovulsants
o Allopurinol (HLA-B5801)
o Sulphur-containing drugs (Septrin, sulfasalazine)
o NSAIDs
• Infection: mycoplasma pneumoniae, HSV/CMV
• Others (rare): vaccination, contrast medium
Clinical features
• Onset of reaction: typically 5-28 days after starting drug
• Prodrome a few days before skin manifestation: URTI-like illness (fever, sore throat, anorexia)
• Skin pain (early feature)
• Painful pruritic morbilliform eruption: first on face / upper trunk —> extremities
• Epidermal necrosis and detachment
o Confluent erythema, atypical targetoid lesions (2 zones only, c.f. EM), dusky
patches (skin death), flaccid blisters prone to erosions, sheet-like epidermal loss
o Nikolsky’s sign +ve (epidermal separation upon gentle pressure on skin surface - DDx: pemphigus, SSSS)
• Mucosal involvement (e.g. oral crusting)
o Involvement: oropharynx (MC), eyes, genitalia and anus, respiratory tract, GI tract (rare)
• Complications
o Secondary bacterial infection (S. aureus, P. aeruginosa) and sepsis (main cause of death)
o Dehydration, pre-renal failure, electrolyte disturbance
o Thermal dysregulation
o ARDS / Respiratory failure
o Multiple organ failure / DIC
o GU tract (hematuria), GI tract (GIB, stricture, ulcer), blindness, oral cavity (oral ulcer)
Prognosis
- Morality: SJS: 1-5%, TEN 25-30%
- SCORTEN score (total 7 points)
o Age > 40
o Presence of malignancy
o HR >120
o BSA > 10%
o Serum urea >10
o Serum glucose >14
o HCO3 <20
- >5 is 90% mortality
Mx:
- stop causative drug
- Initial assessment: Haemodynamic status, BSA, SCROTEN
—> refer ICU if BSA > 10% or SCROTEN>2
- Ix:
o CBC, LRFT, VBG, random glucose, INR, CXR
o Microbiology: Blood C/ST, wound swab C/ST, ± viral culture
o Skin biopsy
- Best supportive care
o Infection: reverse barrier nursing, antibiotics if signs of sepsis (pathogens: S aureus, P aeruginosa)
o Wound care: non-adhesive dressing with antimicrobial properties
o Fluid, electrolytes, nutrition: chart I/O, fluid replacement, Foley, NG tube, PPI
o Mucosal involvement (eye, oral, urogenital): moisturizer (lubricant eyedrop, paraffin), topical steroid, topical
antibiotics
o Pain control (tramadol / morphine / PCA)
• No active therapeutic regimen with unequivocal benefit
o Steroids / IVIG / cyclosporin / anti-TNF (?survival benefit)
• Chart drug allergy in CMS, drug hypersensitivity testing
Drug reaction with eosinophilia and systemic symptoms (DRESS)
Definition: idiosyncratic ADR with long latency and continue for weeks to months after drug withdrawal
Clinical triad
• Fever
• Rash: central facial erythema and edema
• Visceral organ involvement: lymphadenopathy, leucocytosis, eosinophilia, fulminant hepatitis
Diagnostic criteria: regiSCAR criteria
Management:
• Withdraw culprit drug
• Steroids / Cyclosporin
Eczema herpeticum
• Pathogen: HSV
• Risk factors: eczema, chronic topical steroid use
• Clinical features
o Cluster of itchy and/or painful vesicles
o Multiple monomorphic punched out
(crusted) erosions
o Most common on face and neck, can arise
from normal skin or pre-existing skin
disease, e.g. eczema
o Fever and swollen local LN
• Complication: secondary bacterial infection
(Staph / Strep), multiple organ involvement
• Management
o Investigation: skin scraping for viral
detection
o Treatment: IV acyclovir stat
Herpes zoster ophthalmic us
• Pathogen: VZV
• Risk factor: immunocompromised
• Clinical features:
o Headache, fever, malaise
o Hutchinson’s sign: shingles on tip of nose signifies eye involvement (nasociliary branch of V1) - vision loss
• Treatment: acyclovir (oral —> IV)
Erythrodema (Generalized exfoliative dermatitis)
• Definition: “skin failure” - generalised erythema & scaling involving > 90% BSA
• Aetiology: 5 categories
o Exacerbation of pre-existing dermatoses (e.g. atopic eczema, psoriasis,
lichen planus, immunobullous disorders, GvHD)
o Drug eruptions: e.g. antiepileptics, anti-HT (captopril, frusemide),
antibiotics (penicillins, sulphonamides), allopurinol
o Malignancy: e.g. Cutaneous T cell lymphoma (Sezary syndrome)
(MC), Hodgkin’s disease (2nd MC), NHL, leukemias
o Infection: e.g. crusted scabies, dermatophytosis, AIDS
o Idiopathic
• Clinical features
o Generalised bright red erythema, warm and dry
o Complications:
§ Skin failure: hypothermia, dehydration & electrolyte disturbance
§ Infection
§ High-output HF
• Investigations
o CBC D/C, LRFT, ESR ± PBS (Sezary cells), CXR
o Skin biopsy from at least 2 sites: histology, DIF (if suspect immunobullous disease)
o ± age-appropriate malignancy workup (if indicated)
• Management
o Stop precipitating drug
o Supportive management: close monitoring, replace fluid & electrolytes, treat infections
o Intensive topicals (examples for reference)
§ Scalp: betamethasone valerate 0.1% scalp lotion BD
§ Trunk: Synalar (fluocinolone) 0.025% / 0.0125% BD (cream if wet, ointment if dry)
§ Face and flexures: Synalar 0.005% cream BD (use lower potency steroids)
§ Other skincare products: e.g. white soft paraffin, aqueous cream, chlorhexidine wash (if infected)
Erythema nodosum
Erythematous
Tender raised nodule
Panniculitis on biopsy
DDX:
Infection: Streptococcal infection, TB,
mycoplasma pneumoniae
Inflammatory: IBD, SLE
Drugs: sulphonamide, COC
Erythema migrans
Lyme disease
Erythema multiforme
Target lesions (central papule
surround by erythematous ring)
DDX:
Infection: HSV, mycoplasma pneumoniae
Drugs (e.g. penicillin)
Erythema marginatum
Erythematous
Raised, ring-like
Changing pattern with time
DDX:
Rheumatic fever
Pyoderma gangrenosum
Necrotic purulent ulcer, commonly
found in legs
Do NOT debride
DDX:
Inflammatory: IBD, inflammatory arthritis
Malignancy: solid, haematological
Purpura
Aetiology
- Immune (HSP)
- Infectious (meningococcaemia)
- Occlusive (liverdo vasculopathy —> Tx: antiplatelet, anticoagulation, fibrinolytic therapy)
Palpable Purpura = inflammatory vasculitis / vasculopathy; end-stage ->
ulceration, necrosis, bullae, infarct (do NOT Bx these areas)
Ix:
- Baseline blood tests, blood & urine gram stain c/st, urine multistix
- ASOT, throat swab
- Hepatitis & HIV serology
- Autoimmune markers
Tx:
- None if asymptomatic
- General: RICE, pressure stockings
- Medical: Colchicine, dapsone, antihistamine, NSAIDS, prenidolone, MTX, azathioprine
Haemorrhagic Bullae ddx
- Disseminated Herpes zoster
- Meningococcaemia
- Gonococcaemia
- Septic emboli
- Bullous drug eruption
- Coagulopathy
Purpura fulminans
-Due to DIC (causing protein C deficiency)
-Meningococcaemia!!!
-Empirical systemic antibiotics <30mins, debride dead tissue, IVIG, FFP, ICU
