Dermatology

Question 1

Erythema multiforme epidemiology

Answer 1

Adults 20-40yo
Can affect any age group

Question 2

Erythema multiforme distribution

Answer 2

Symmetrical, typically on extremities
< 10% TBSA

Question 3

Erythema multiforme development

Answer 3

Quickly over a 24 hour period
First appear on dorsums of hands and feet –> spread along limbs –> trunk

Question 4

Clinical erythema multiforme

Answer 4

Start: well demarcated red/pink macules, mildly pruritis –> blistering/crusting in centre of lesions

Target lesions with 3 concentric zones
- dark red centre with blister/crust
- raised pink oedematous ring
- bright red ring

Question 5

Erythema multiforme forms

Answer 5

Minor: no prodromal illness or mucous membrane involvement
Major: prodromal Sx (fever, chills, lethargy, GI upset, arthralgia) –> precede lesions by 1-14 days + mucosal involvement (blisters –> break to painful ulcers)

Question 6

Erythema multiforme aetiology

Answer 6

90%: infection
- MC = HSV1 esp. affecting lip
- mycoplama pneumonia
- VZV, Hep viruses, HIV, CMV, poxvirus
- dermatophyte infections

Drugs
- NSAIDs, barbituates, penicillins, sulphonamides, antiepileptics, phenothiazines

Question 7

Dx Erythema multiforme

Answer 7

clinical

may be supported by skin biopsy histology
Ix to ID causative infection

Question 8

Tx of Erythema multiforme

Answer 8

Targeted at possible cause e.g., HSV or mycoplasma pneumoniae or cessation of offending drug

Skin lesions often require no Tx
Symptomatic Tx can be topical corticosteroids and anti-histamines and mouthwashes with LA and antiseptic

Question 9

Prognosis Erythema multiforme

Answer 9

Good
Self limiting: 2-3 weeks for minor and 6 weeks for major

recurrence possible esp. if assoc. with HSV

Question 10

Dx not to miss as DDx for Erythema multiforme

Answer 10

toxic epidermal necrolysis (TEN) or Stevens-Johnson syndrome (SJS) can present with target lesions in early cause of disease

Question 11

What is cutaneous vasculitis

Answer 11

Clinicopathologic process characterised by inflammation of the blood vessels in the skin. With marked involvement, it leads to ischaemia of the overlying or underlying tissues.

can be a part of systemic vasculitis where other organ systems can be involved.

Question 12

Mechanisms of cutaneous vasculitis

Answer 12

Direct injury to vessel wall by infective agent

Indirect injury via deposition of immune complexes activating complement components

Indirect injury by activation of antibodies

Delayed HS reaction

Question 13

Large vessel vasculitis e.g.,

Answer 13

Takayasus arteritis
Giant cell arteritis

Question 14

Medium vessel vasculitis

Answer 14

Polyartheritis nodosa
Kawasaki disease
ANCA-associated

Question 15

Small vessel vasculitis

Answer 15

Microscopic polyangiitis, livedo vasculitis, Henoch-Schonlein purpura, and cryoglobulinaemic vasculitis

Question 16

Leukoclastic vasculitis (acute) presentation

Answer 16

Palpable purpura (bleeding under the skin), petechiae, ulceration and necrosis

Systemic signs can include fever, arthralgia, and gastrointestinal upset.

Symptoms usually resolve after 2-3 weeks.

Question 17

Dx cutaneous vasculitis

Answer 17

Diagnosis is made on clinical appearance and confirmed with biopsy. Other investigations focus on identifying systemic involvement and the underlying cause. Kidney function and urine dipstick may indicate involvement of the kidneys by the presence of protein and blood. FBC can detect blood disorders, autoimmune screen (ANA, ANCA, ENA, RF) may indicate SLE or other autoimmune disorders, cryoglobulins detect antibodies that precipitate in the cold, and electrophoresis can detect blood disorders such as multiple myeloma. Anti-streptococcal antibodies and hepatitis B and C serology can detect bacterial and viral infection. Anti-neutrophil cytoplasmic antibodies (ANCA) are increased in patients with systemic vasculitis particularly medium sized vessel vasculitis such as granulomatosis with polyangiitis or eosinophilic granulomatosis with polyangiitis. Up to 75% of cases are idiopathic in nature and no cause is identified.