Makindo Medical Notes

Related Subjects: |Cellulitis |Impetigo |Pyoderma gangrenosum |Pemphigus Vulgaris |Toxic Epidermal Necrolysis |Stevens-Johnson Syndrome |Necrotising fasciitis |Gas Gangrene (Clostridium perfringens) |Anatomy of Skin |Skin Pathology and lesions |Skin and soft tissue and bone infections

🦵 Cellulitis is a common bacterial infection of the skin and subcutaneous tissues. It is most often due to Streptococcus pyogenes or Staphylococcus aureus. ⚠️ Early recognition and treatment are essential to prevent systemic spread. 👉 Bilateral red legs are common, but if legs are red and cool/normal in temperature, cellulitis is unlikely.

📖 About Cellulitis

• Infection of the skin and underlying tissues, presenting with erythema, swelling, warmth, and tenderness.
• Usually affects the legs, but can occur on the arms, face, or other body sites.
• Rarely life-threatening, but severe untreated cases can progress to sepsis or necrotizing infection.
• Most commonly caused by Streptococcus pyogenes and Staphylococcus aureus.

⚠️ Risk Factors

• Skin trauma (cuts, insect bites, burns, surgical wounds).
• Lymphoedema, tinea pedis, or chronic venous insufficiency.
• Obesity, chronic oedema, or immunosuppression.
• Diabetes and peripheral vascular disease increase risk of severe infection.

👩‍⚕️ Clinical Features

• Red, swollen, warm, and tender skin (usually unilateral).
• Lower legs are most commonly affected.
• May have systemic features: fever, malaise.
• Look for skin entry points (toe webs, wounds, ulcers).
• Draw round the erythematous edge with a pen to monitor spread.

🔍 Differential Diagnosis

• Deep vein thrombosis (DVT).
• Lymphangitis, abscess, venous ulcers, stasis dermatitis.
• Necrotizing fasciitis, gas gangrene, or osteomyelitis (serious mimics).

🚨 Severe Cellulitis Indicators

• Rapid spread of erythema.
• High fever (>38°C), hypotension, or tachycardia.
• Involvement of face or hand (urgent sites).
• No improvement with oral antibiotics.
• High-risk comorbidities (asplenia, cirrhosis, neutropenia, cardiac or renal failure).

📊 Cellulitis Classification

🦠 Common Pathogens

• Staphylococcus aureus (most common).
• Group A beta-haemolytic streptococci.
• Anaerobes in diabetic/ischaemic limb infections.

👥 Patients at Higher Risk

• Diabetics (especially diabetic foot infections).
• Immunocompromised patients (chemotherapy, HIV).
• Peripheral vascular disease and chronic venous insufficiency.

🧪 Diagnostic Approach

• Bloods: FBC (↑WCC), ESR, CRP.
• U&E + Glucose: Check renal function and diabetes screen.
• Blood cultures: If pyrexial or unwell.
• X-ray: If osteomyelitis or deep tissue infection suspected.

💊 Management of Cellulitis

• Mild–moderate: Oral antibiotics (e.g., flucloxacillin 500mg–1g qds). Penicillin allergy → clarithromycin or doxycycline.
• Moderate–severe: IV benzylpenicillin + flucloxacillin. Penicillin allergy → teicoplanin.
• Diabetic foot/severe cases: IV co-amoxiclav (or clindamycin if allergic).
• Take cultures if pus or wounds are present before starting antibiotics.
• Consider urgent surgical referral for necrotizing fasciitis or deep abscess.
• Monitor patients with chronic wounds closely (diabetic podiatry + microbiology input).