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Flashcards in Dermatology Deck (34)
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1
Q

What would be the likely cause of a edematous papular rash on the lower legs with target lesions and an extensor distribution?

A

Erythema multiforme. Usually follows infection or new drug. Palms and lips can also be involved.

2
Q

What would be the likely cause of a purpuric rash on the lower legs with an unwell, febrile patient?

A

Meningococcal septicaemia.

3
Q

What would be the likely cause of a rash on the lower legs with purplish flat topped papules.

A

Lichen planus. Possibly this is autoimmune mediated.

4
Q

What would be the likely cause of a rash on the lower legs with individual round lesions?

A

Insect bites - especially if history suggestive.

5
Q

Cause of rash in meningococcal septicaemia

A

Vascular occlusion and localised areas of inflammation and necrosis.
The lesions are purpuric (purplish, non-compressible) due to leakage of red blood cells out of damaged vessels into the dermis and sub-cutis.

6
Q

Progression of rash in meningococcal septicaemia.

A

The lesions start as red areas and develop rapidly into purple areas, often with a reticulate (network) pattern or an angular, stellate (star-shaped) pattern. Blistering and then ulceration is common as the necrosis develops.

7
Q

Appearance of lichen planus

A

The lesions may have a fine white network pattern on the surface – called Wickham’s striae.

May be a white network inside the mouth, usually on the buccal mucosa.

8
Q

What is the most likely cause of a purplish rash on the lower legs?

A

Vasculitis.

9
Q

List causes of purplish lower leg rashes

A
Cutaneous vasculitis
Erythema multiforme
Meningococcal septicaemia
Infective endocarditis
Insect bites
Coagulopathy as in myeloma.
10
Q

What investigations would you do to rule out vasculitis as a cause of a purplish lower leg rash.

A

U&E - renal damage from vasculitis
LFT - hepatitis cause of vasculitis
Urine microscopy - to confirm dipstick findings
Skin biopsy with immunofluorescence - for vasculitis
ANA, RF - for connective tissue disease cause of vasculitis
ASOTitre (Streptococcal infection) - for infection cause of vasculits
Hepatitis B & C serology - for infection cause of vasculitis

11
Q

What investigations would you do to rule out infective endocarditis as a cause of purplish lower leg rash?

A

Chest X ray - Heart size (Inf Endo),

Blood culture if patient generally unwell or with marked pyrexia - infective endocarditis, meningococcus

12
Q

Common causes of cutaneous vasculitis

A

Streptococcal infection
Drug reaction, especially analgesics and antibiotics
Collagen diseases (RA, SLE)
Malignancy

13
Q

Vitiligo

A

well demarcated patches of depigmented skin
the peripheries tend to be most affected
trauma may precipitate new lesions (Koebner phenomenon)

14
Q

Conditions associated with vitiligo

A
type 1 diabetes mellitus
Addison's disease
autoimmune thyroid disorders
pernicious anaemia
alopecia areata
15
Q

Management of vitiligo

A

sun block for affected areas of skin
camouflage make-up
topical corticosteroids may reverse the changes if applied early
there may also be a role for topical tacrolimus and phototherapy, although caution needs to be exercised with light-skinned patients

16
Q

What is the difference between lichen planus and lichen sclerosis?

A

planus: purple, pruritic, papular, polygonal rash on flexor surfaces. Wickham’s striae over surface. Oral involvement common
sclerosus: itchy white spots typically seen on the vulva of elderly women

17
Q

What drugs causes lichenoid eruptions?

A

gold
quinine
thiazides

18
Q

How do you treat lichen planus?

A

topical steroids are the mainstay of treatment

extensive lichen planus may require oral steroids or immunosuppression

19
Q

How do you treat cellulitis?

A

Using flucloxacillin

20
Q

Acne rosacea

A

Acne rosacea is a chronic skin disease of unknown aetiology

Features
typically affects nose, cheeks and forehead
flushing is often first symptom
telangiectasia are common
later develops into persistent erythema with papules and pustules
rhinophyma
ocular involvement: blepharitis

21
Q

Treatment for acne rosacea

A

opical metronidazole may be used for mild symptoms (i.e. Limited number of papules and pustules, no plaques)
more severe disease is treated with systemic antibiotics e.g. Oxytetracycline
recommend daily application of a high-factor sunscreen
camouflage creams may help conceal redness
laser therapy may be appropriate for patients with prominent telangiectasia

22
Q

What is the likely cause of a small round patch of hair loss in a 23 yr old man?

A

Alopecia areata

23
Q

What is alopecia areata

A

Alopecia areata is a presumed autoimmune condition causing localised, well demarcated patches of hair loss. At the edge of the hair loss, there may be small, broken ‘exclamation mark’ hairs

24
Q

Prognosis of alopecia areata

A

Hair will regrow in 50% of patients by 1 year, and in 80-90% eventually. Careful explanation is therefore sufficient in many patients. Other treatment options include:
topical or intralesional corticosteroids
topical minoxidil

25
Q

What is the name and vitamin deficiency causing diarrhoea, confusion and eczematous skin

A

Pellagra, caused by niacin (B3) deficiency

26
Q

Examples of type 1 hypersensitivity reactions

A
  • Anaphylaxis

* Atopy (e.g. asthma, eczema and hayfever)

27
Q

Mechanism of type 1 hypersensitivity reaction

A

Antigen reacts with IgE bound to mast cells

28
Q

Examples of type 2 hypersensitivity reactions

A
  • Autoimmune haemolytic anaemia
  • ITP
  • Goodpasture’s syndrome
  • Pernicious anaemia
  • Acute haemolytic transfusion reactions
  • Rheumatic fever
  • Pemphigus vulgaris / bullous pemphigoid
29
Q

Mechanism of type 2 hypersensitivity reaction

A

IgG or IgM binds to antigen on cell surface

30
Q

Mechanism of type 3 hypersensitivity reaction

A

Free antigen and antibody (IgG, IgA) combine

31
Q

Examples of type 3 hypersensitivity reactions

A
  • Serum sickness
  • Systemic lupus erythematosus
  • Post-streptococcal glomerulonephritis
  • Extrinsic allergic alveolitis (especially acute phase)
32
Q

Mechanism of type 4 hypersensitivity reaction

A

T-cell mediated

33
Q

Examples of type 4 hypersensitivity reactions

A
  • Tuberculosis / tuberculin skin reaction
  • Graft versus host disease
  • Allergic contact dermatitis
  • Scabies
  • Extrinsic allergic alveolitis (especially chronic phase)
  • Multiple sclerosis
  • Guillain-Barre syndrome
34
Q

Features of necrotising fasciitis

A

acute onset
painful, erythematous lesion develops
extremely tender over infected tissue