Derm - Skin Infections

Question 1

which skin layers are affected in cellulitis? what are the most common causative organisms?

Answer 1

Dermis + subcutaneous tissue

1. Staph. aureus
2. Strep. pyogenes

Question 2

describe the usual presentation of cellulitis

Answer 2

• pain + tenderness
• swelling
• erythema + skin increased temp.
• +/- blisters or bullae
• +/- fever, malaise, nausea, rigors

Question 3

how would you grade severity of cellulitis?

Answer 3

Eron classification system:

1. grade I: no signs of systemic toxicity, no uncontrolled co-morbidities
2. grade II: pt is systemically unwell or pt systemically well but with co-morbidity that could complicate or prolong infection, e.g. PAD, chronic venous insufficiency , morbid obesity
3. grade III: pt is systemically unwell e.g. acute confusion, tachycardia, tachypnoea, hypotension or unstable co-morbidities
4. grade IV: pt has sepsis syndrome or severe life-threatening infection such as necrotising fasciitis

Question 4

how would you manage a pt with grade I cellulitis

Answer 4

1. FLUCLOXACILLIN PO 7 days (clarithromycin if penicillin allergy)
2. paracetamol/ibuprofen for analgesia
3. adequate fluids
4. treat risk factors, e.g. fungal skin infection

Question 5

what is erysipelas? how can it be differentiated from cellulitis?

Answer 5

Superficial form of cellulitis involving dermis + upper subcutaneous tissue (St Anthony’s fire)

Cellulitis: poorly demarcated borders, usually lower limb
Erysipelas: sharply demarcated borders, usually face or leg

Question 6

a child comes in with rapidly spreading tiny pustules and honey-coloured crusted plaques on face + enlarged regional LNs. what is the likely diagnosis and causative organism? how would you treat this?

Answer 6

Non-bullous IMPETIGO. Usually Staph. aureus of Strep. pyogenes if skin is breached.

Management:

• good hygiene measures, time of school/work
• topical FUSIDIC ACID (TDS for 7 days) or topical MUPIROCIN if MRSA
• oral FLUCLOXACILLIN if extensive or resistant infection

Question 7

how would you treat a pt with a tinea infection (ringworm)?

Answer 7

Imidazole cream BD, continuing for 1-2 weeks after skin has healed, e.g. CLOTRIMAZOLE, ECONAZOLE, KETOCONAZOLE, MICONAZOLE

Question 8

what is the causative agent of chicken pox? how would you treat?

Answer 8

varicella zoster virus

Paracetamol for pain and fever, antihistamines and emollients for pruritis

Question 9

how would you treat shingles if required?

Answer 9

ACICLOVIR 5x/day for 7 days. keep rash clean and dry

If within 72 hrs of rash onset and >50, non-truncal involvement, moderate-severe pain or rash, ophthalmic involvement
or immunocompromise