Dermatology Flashcards
Alopecia areata
incidence: 1%
trigger: emotional stress
pathogenesis: chronic AI disorder with T cells targeting anagen hair follicles with transition into the telogen phase
associations: atopy, nail changes, cataracts/lens opacification, AI diseases, T21
family history: 10-20%
clinical: rapid, complete hair loss in round/ oval patches
- no inflammation so the scalp is smooth and quite bald
- spontaneous resolution 6-12 mths
treatment: usually reassurance only
Congenital bullous ichthyosiform erythroderma
genetics: AD defect in keratin 1 or 10 on chromosome 12p
clinical:
- birth: generalised erythroderma/severe hyperkeratosis with hyperkeratotic ridges over joint flexures (axillary, popliteal, CF, neck, hips)
- recurrent blistering may be widespread in neonates
treatment: difficult, AB
Contact dermatitis
pathophysiology: T-cell-mediated hypersensitivity reaction from Ag on skin surface triggering activation of sensitised T cells within 8-12hours
clinical: erythematous, pruritic, eczematous dermatitis which if severe can be vesiculobullous
treatment: treat for 10-14 days
- steroids (if <10% of skin and not spreading may use ointment)
- symptomatic treatment: antihistamines, wet dressings
Erythema marginatum
cause: acute rheumatic fever
time: early in disease
clinical: evanescent, pink or faintly red, nonpruritic annulare rash involving the trunk and sometimes the limbs, but not the face usually occurs early in the course of ARF
- lesions disappear and reappear in a matter of hours
- often associatred with acute carditis
Erythema Multiforme
definition: acute immune-mediate condition characterised by target-like lesions on skin or mucosa
prevalence: <<1%, age 20-40yrs
causes:
- infection/immunisations (90%): most commonly HSV, mycoplasma
- malignancies
- drugs (<10%): NSAIDs, sulfonamides, AED, AB (most commonly penicillin)
- AI disease
clinical: target lesions in symmetrical distribution on extensor surfaces or extremities
- lasting 5 days to 2 weeks
- prodromal syndromes are uncommon
Infantile haemangiomas
definition: vascular dysplasia from proliferating capillary endothelium (angioblastic cells)
prevalence: 10% children <1 yr
natural history: grow in first 6- 12 months then involute 10% per year after
- 50% resolved 5 years, 70% by 7 years, 90% by 9 years
- 10- 40% will have residual changes (telangiectasia, pallor, atrophy, skin redundancy)
indications for treatment:
- Kasabach-Merrit sx
- affecting the eye/airway/lip/ear/nasal cartilage
- recurrent bleeding, ulceration, infection
- high CO
treatment:
- 1st line: PO propranolol 1-2mg/kg/day for 3-6 months (60% effective)
- other: IFN-g, laser, surgery
Pimecrolimus
use: second-line agent for short-term and intermittent treatment of mild to moderate atopic dermatitis in non-immunocompromised patients
mechanism: topical calcineurin inhibitors
benefit: does NOT cause skin atrophy
adverse reactions: facial edema, headache, fever, pruritis, folliculitis, discolouration, nausea, burning, coryza, LN, anaphylactoid reaction
Rash of zinc deficiency
causes:
acquired: breast milk deficient in zinc (mother with Crohn’s)
inherited: AR acrodermatitis enteropathica hereditary zinc deficiency
- weaning from breast to cow’s milk
clinical:
- cutaneous eruption: vesiculobullous, eczematous, dry, scaly, or psoriasiform skin lesions symmetrically distributed in the perioral, acral, perineal areas, cheeks, knees and elbows
- diarrhea, stomatitis, glossitis, paronychia, nail dystrophy, growth retardation, irritability
diagnosis: low zinc level
treatment: oral zinc sulfate 1-2mg/kg/day
Rashes
Staph perianal disease
organism: group A B-haemolytic streptococcus
transmission: digital contamination from an infected oropharynx
incidence: male>females, 3-4yrs
clinical: 3 presentations
1. bright pink erythema extending 2-3 cm from the anus, skin tender but not indurated
2. painful anal fissuring and dried mucoid discharge of perianal skin
3. erythematous psoriasiform eruption extending several cm from anal rim with yellow superficial crusting at the peripheral border with satellite crusted lesions
- pain on defecation universal complaint
diagnosis: perianal swab
treatment: penicillin V 50mg/kg/day + topical mupurocin BD 10/7
Staphylococcus Scalded Skin Syndrome
incidence: day 3 to 5 years
pathology: staph aureus exfoliative toxins
pathogenesis: toxins act on the granulosa of the epidermis causing cleavage of desmoglein complex 1
clinical: malaise, fever, irritability then rash
- scarlatiniform erythema diffuse to flexural and periorifical areas, conjunctivitis, flaccid blisters, erosions, nikolsky sign
diagnosis:
- histology: cleavage plane in the lower stratum granulosum with minimal inflammation/necrosis
progression:
- day 2-5: desquamation , day 10-14: healing w/o scarring
Steven Johnson Syndrome
Toxic Epidermal Necrosis
definition: SJS, Toxic Epidermal Necrolysis, SJS/TEN overlap syndrome
pathogenesis: uncertain etiology with desquamative lesions of skin/mucous membranes
distribution: <10% epidermis SJS, >30% TEN, 10-30% overlap SJS/TEN
cause:
- infections: mycoplasma
- drugs: sulfonamides, NSAIDs, Ab, AEDs especially lamotrigine
clinical:
- prodrome of fever and influenza-like symptoms 1-3 days
- mucocutaneous/skin vesicular and bullous lesions followed by sloughing
- may be multiorgan involvement
- resolved 2-4 weeks
risk factors: HIV, genetic factors, viral infections, immunologic diseases
diagnosis: clinical, histology only supportive
management: w/d potentially causative agents, AB, IVIg
mortality: SJS 1-3%, TEN 25-35%
Sturge Weber Syndrome
cause: sporadic mutation GNAQ gene
clinical: port wine stain, glaucoma, seizures, MR, ipsilateral leptomeningeal angioma
symptoms: serizures 80%, headache 60%, DD 50%, glaucoma 50%, hemianopsia 50%, hemiparesis 50%
type 1: (most common) facial/leptomeningial angiomas, glaucoma
type 2: facial angioma, possible glaucoma
type 3: leptomeningeal angioma
pathophysiology: error in mesodermal/ectodermal development
- port wine stain: abundance of capillaries around opthalmic branch trigeminal nerve
Tinea
organism: dermatophyte fungi
clinical: pruritic erythematous papules, pustules, annular or geographical lesions
- unilateral/asymmetrical
treatment: topical antifungals (whitfield’s ointment, Imidazole creams) for small patches
- oral griseofulvin for severe skin infection or hair infections
Urticaria pigmentosa
(mastocytosis)
aka: maculopapular cutaneous mastocytosis
pathogenesis: aggregates of mast cells in the dermis
classic infantile type: lesions erupt 1st several months-2 yrs
- bullous/urticarial lesions that become hyperpigmented
- larger nodular lesions, like mastocytomas may have orange-peel texture
- stroking to the nodule causes urtication (Darier sign) from histamine release
adult type: caused by mutation in stem cell factor
- does not resolve and new lesions continue to develop throughout adult life
Topical steroids
weak: hydrocortisone 0.5% or 1%
- face and nappy area
moderate: betamethasone valerate 0.02% or propionate 0.05% or 1%
- body
strong: mometasone 0.1% @ night (elocon)
- to body only
Infantile haemangiomas
definition: benign tumours of vascular endothelium
prevalence: 10% of <1 year olds
clinical: 95% involute spontaneously after period of initial growth
- growth 6-12 months
- 50% by 5 yrs
- 70% by 7 yrs
- 90% by 9 yrs
indications for treatment:
- large/rapidly growing
- lesions in the lip/nose/periorbital region/airway/liver/GI
- risk of ulceration, scarring or disfigurement
treatment:
- topical (localised/uncomplicated): topical beta blockers, CS, imiquimod
- propranolol
Incontinentia pigmenti
genetic: IKBKG gene with X-linked activation in females (lethal in males)
definition: hereditarable, multisystem ectodermal dermatologic, dental, and ocular abnormalities
clinical:
- 1st stage birth- erythematous linear streaks and plaques of vesicles that are most pronounced on limbs and cirumferentially on the trunk. Resolves 4 mths
- 2nd stage: blisters become dry hyperkeratotic, forming verrucous plaques. Involute by 6 mths
- 3rd stage: hyperpigmentation on trunk with macular whorls, reticulated patches, flecks, streaks that folllow blaschko line. Fade by early adolescence and often disappear by age 16
- 4th stage: hairless, anhidrotic, hypopigmented patches
associations:
- alopecia 40%
- dental anomalies 80%: hypodontia, conical teeth
- CNS: MR, seizures, microcephaly, spasticity in 1/3
- ocular anomalies in >30%
diagnosis: clinical gournds; Wood lamp highlight pigmentary abnormalities
Telogen effuvium
definition: sudden loss of large amount of hair
pathogenesis: premature conversion of growing, or anagen hairs to resting, or telogen hairs
causes: 6wks-3 mo after precipitating cause
- eg. childbirth, fever, severe weight loss, blood loss, psychiatric stress
prognosis: ormal hair growth will return within 6 months
Acute palmoplantar eczema
(pompholyx)
prevalence: young adults
clinical: intensly pruritic vesicular eruption to palms/soles
- vesciles/bullae for several weeks which resolve with desquamation
treatment: topical steroids, calcineurin inhibitors
Eczema
age: early onset
incidence: 15%
clinical: pruritis, eczema, atopy, xerosis
pathogenesis:
- defect stratum cornea: outer defect
- filaggrin deficiency: aligns keratin, moisturises
treatment: eczema should resolve within 2 weeks
Psoriasis
incidence: 1%
associations: arthritis in 40%
risk factors: smoking, stress, skin trauma
treatment: topical, PT (UVB), systemic tx
- NEVER use systemic steroids (pustular flare)
prognosis: increased risk metabolic disorders
PHACE syndrome
P: posterior fossa malformation
H: haemangioma
A: arterial anomalies
C: CV anomalies
E: eye anomalies
S: sternal cleft
Sebaceous Naevi
incidence: 0.3%
appearance: pink/orange plaques with velvety surface
- no hair
location: majority head/necks
associations: epidermal naevus syndrome (seizures, ID, spastic hemiparesis, deafness, CNS abnormalities)
treatment: excision before puberty
Becker naevus
appearance: asymmetrical persistant areas of pigmentation presenting in childhood/adolescence
risk factors: increased androgen sensitivity
sex: M:F = 5:1
Ossification Centres
C: capitellum (age 1)
R: radial head (age 3)
I: internal epicondyle (age 5)
T: trochlear (age 7)
O: olecranon (age 9)
E: external epicondyle (age 11)
