Cellulitis and Erysipelas

Question 1

Define cellulitis

Answer 1

Acute non-purulent spreading infection of the subcutaneous tissue -> overlying skin
inflammation

Question 2

What are the causes/risk factors of cellulitis?

Answer 2

• Streptococcus pyogenes
• Staphylococcus aureus (including MRSA)
• Haemophilus influenzae (orbital cellulitis)

Risk Factors
• IV cannulation
• Ulcers/wounds
• Insect bites
• Sebaceous cysts
• Surgery
• Fissures
• Poor hygiene
• Venous insufficiency
• Chronic leg oedema
• Diabetes

Question 3

What are the signs and symptoms of cellulitis?

Answer 3

• Erythematous
• Oedema
• Warm
• Tender
• Indistinct margins
• Pyrexia

Periorbital
• Painful, red, swollen eyelids

Orbital
• Painful/limited eye movements
• Proptosis
• Impaired acuity

Question 4

What investigations are carried out for cellulitis?

Answer 4

• FBC - raised WCC
• purulent focus culture and molecular diagnostic procedures - growth of typical pathogen (e.g., Staphylococcus aureus)
• interdigital space culture - growth of typical pathogen (e.g., Streptococcus pyogenes)
• skin aspiration with culture and molecular diagnostic procedures - (e.g., Streptococcus pyogenes)
• blood culture - (e.g., Streptococcus pyogenes)
• skin biopsy - histological evidence of acute inflammation and presence of micro-organisms
• plain film x-ray - lytic or periosteal changes in subjacent osteomyelitis
• ultrasound - fluid collection seen if abscess is present
• CT scan - fluid collection seen if abscess is present; orbital or preseptal (periorbital) cellulitis
• MRI - contrast enhancement, thickening of deep fasciae with fluid collection in NF; evidence of osteomyelitis if present

Question 5

Define erysipelas

Answer 5

Erysipelas is a distinct form of superficial cellulitis with notable lymphatic involvement and is raised, sharply demarcating it from uninvolved skin.