Infectious diseases for MRCP Part 1

A 60-year-old man has 2 days of a spreading, hot, red, tender area over his left shin with a low-grade fever. There is a small area of athlete's foot between the toes. He is systemically well with normal observations. What is the most likely diagnosis?

1. Necrotising fasciitis A surgical emergency with pain out of proportion. Unilateral spreading hot red tender skin with a portal of entry, systemically well must be excluded.
2. Contact dermatitis An inflammatory rash from an allergen. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes it a consideration.
3. Cellulitis correct Correct. Unilateral spreading hot, red, tender skin with a portal of entry is cellulitis.
4. Venous eczema or stasis dermatitis Often bilateral and itchy rather than infected. Unilateral spreading hot red tender skin with a portal of entry, systemically well separates it.
5. Deep abscess A collection needing drainage. Unilateral spreading hot red tender skin with a portal of entry, systemically well points elsewhere.

The point: Cellulitis is an acute bacterial infection of the deep dermis and subcutaneous tissue, usually caused by Streptococcus pyogenes or Staphylococcus aureus. It presents with a spreading area of hot, red, swollen and tender skin, most often on the lower leg, sometimes with fever and malaise, and a portal of entry such as a break in the skin, tinea pedis, ulcer or lymphoedema. It is a clinical diagnosis; the affected area is marked to track progression, and swabs are taken only if the skin is broken. First-line treatment is oral flucloxacillin, with clarithromycin or doxycycline for penicillin allergy, and admission for intravenous antibiotics if there are systemic features, rapid spread, immunosuppression or failure of oral treatment. The Eron classification helps decide the setting of care. The key differentials are a deep vein thrombosis (which can coexist), venous eczema or stasis dermatitis (often bilateral and itchy rather than infected), and the emergency of necrotising fasciitis, which is suggested by pain out of proportion, rapid progression, systemic toxicity, skin necrosis or crepitus and needs urgent surgical review. Bilateral lower-leg redness is rarely cellulitis and usually reflects venous disease. Recurrent cellulitis in a limb with lymphoedema may warrant antibiotic prophylaxis.

Source: NICE NG141 — cellulitis and erysipelas: antimicrobial prescribing NICE · tier 1, national regulator or guidance

A 60-year-old man has 2 days of a spreading, hot, red, tender area over his left shin with a low-grade fever. There is a small area of athlete's foot between the toes. He is systemically well with normal observations. What is the most appropriate investigation?

1. Doppler ultrasound if a deep vein thrombosis is suspected To exclude the mimic. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes it clarifying.
2. Clinical assessment with marking of the area correct Correct. Cellulitis is a clinical diagnosis, and marking the area tracks the response.
3. Swab only if the skin is broken Targets antibiotics when there is a wound. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes it selective.
4. Urgent surgical assessment if necrotising fasciitis is possible For the emergency. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes it decisive.
5. Inflammatory markers and white cell count Support infection and severity. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes them useful.

The point: Cellulitis is an acute bacterial infection of the deep dermis and subcutaneous tissue, usually caused by Streptococcus pyogenes or Staphylococcus aureus. It presents with a spreading area of hot, red, swollen and tender skin, most often on the lower leg, sometimes with fever and malaise, and a portal of entry such as a break in the skin, tinea pedis, ulcer or lymphoedema. It is a clinical diagnosis; the affected area is marked to track progression, and swabs are taken only if the skin is broken. First-line treatment is oral flucloxacillin, with clarithromycin or doxycycline for penicillin allergy, and admission for intravenous antibiotics if there are systemic features, rapid spread, immunosuppression or failure of oral treatment. The Eron classification helps decide the setting of care. The key differentials are a deep vein thrombosis (which can coexist), venous eczema or stasis dermatitis (often bilateral and itchy rather than infected), and the emergency of necrotising fasciitis, which is suggested by pain out of proportion, rapid progression, systemic toxicity, skin necrosis or crepitus and needs urgent surgical review. Bilateral lower-leg redness is rarely cellulitis and usually reflects venous disease. Recurrent cellulitis in a limb with lymphoedema may warrant antibiotic prophylaxis.

Source: NICE NG141 — cellulitis and erysipelas: antimicrobial prescribing NICE · tier 1, national regulator or guidance

A 60-year-old man has 2 days of a spreading, hot, red, tender area over his left shin with a low-grade fever. There is a small area of athlete's foot between the toes. He is systemically well with normal observations. What is the most appropriate management?

1. Clarithromycin or doxycycline for penicillin allergy An effective alternative. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes it flexible.
2. Oral flucloxacillin first line correct Correct. Oral flucloxacillin is first-line for uncomplicated cellulitis in a systemically well patient.
3. Urgent surgery for necrotising fasciitis The surgical emergency. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes it life-saving.
4. Elevate the limb and treat the portal of entry Elevating the limb and treating the tinea pedis portal aids recovery and prevents recurrence, and unilateral spreading hot red tender skin with a portal of entry, systemically well here points elsewhere.
5. Intravenous antibiotics and admission for systemic or severe disease Guided by the Eron class. Unilateral spreading hot red tender skin with a portal of entry, systemically well makes it an escalation.

The point: Cellulitis is an acute bacterial infection of the deep dermis and subcutaneous tissue, usually caused by Streptococcus pyogenes or Staphylococcus aureus. It presents with a spreading area of hot, red, swollen and tender skin, most often on the lower leg, sometimes with fever and malaise, and a portal of entry such as a break in the skin, tinea pedis, ulcer or lymphoedema. It is a clinical diagnosis; the affected area is marked to track progression, and swabs are taken only if the skin is broken. First-line treatment is oral flucloxacillin, with clarithromycin or doxycycline for penicillin allergy, and admission for intravenous antibiotics if there are systemic features, rapid spread, immunosuppression or failure of oral treatment. The Eron classification helps decide the setting of care. The key differentials are a deep vein thrombosis (which can coexist), venous eczema or stasis dermatitis (often bilateral and itchy rather than infected), and the emergency of necrotising fasciitis, which is suggested by pain out of proportion, rapid progression, systemic toxicity, skin necrosis or crepitus and needs urgent surgical review. Bilateral lower-leg redness is rarely cellulitis and usually reflects venous disease. Recurrent cellulitis in a limb with lymphoedema may warrant antibiotic prophylaxis.

Source: NICE NG141 — cellulitis and erysipelas: antimicrobial prescribing NICE · tier 1, national regulator or guidance