Dermatology
Question 290 of 300
A 12 year old boy is brought to the Emergency Department with a 2 day history of an itchy rash around the nose. You see a yellow crust over several lesions around the nose and diagnose impetigo. His mother asks "When can he return to school?".
Answer:
Patient advice:- Reassure the person that impetigo usually heals completely without scarring, and that serious complications are rare.
- Advise the person, and their carers if appropriate, about good hygiene measures to aid healing and reduce the spread of impetigo to other areas of the body and to other people.
- Inform the person of Public Health England exclusion recommendations:
- Children and adults should stay away from school and other childcare facilities or work until lesions are healed, dry and crusted over or 48 hours after initiation of antibiotics.
- Food handlers are required by law to inform employers immediately if they have impetigo.
Impetigo
Dermatology
Last Updated: 12th February 2021
Impetigo is a common superficial bacterial infection of the skin. Impetigo affects all age groups but is most common in young children. The two main clinical forms are non-bullous impetigo (accounts for the majority of cases - about 70%) and bullous impetigo.
Causes
Transmission of impetigo occurs directly through close contact with an infected person or indirectly via contaminated objects such as toys, clothing, or towels. Bacteria enter the skin through breaks caused by minor trauma (such as insect bites or scratches) or underlying skin conditions (such as eczema or scabies). The incubation period is 4–10 days. Non-bullous impetigo is caused by Staphylococcus aureus, Streptococcus pyogenes or a combination of both. Bullous impetigo is caused by Staphylococcus aureus; bullae form when exfoliative toxins produced by S. aureus cause loss of cell adhesion in the superficial epidermis.
Complications
Complications of impetigo are uncommon and include:
- Acute glomerulonephritis (following streptococcal impetigo)
- Cellulitis
- Staphylococcal scalded skin syndrome
- Lymphangitis
- Osteomyelitis and septic arthritis
- Septicaemia
- Scarlet fever, urticaria and erythema multiforme (following streptococcal infection)
Clinical features
- Non-bullous impetigo
- Lesions begin as thin walled vesicles or pustules (seldom seen on clinical examination as they rupture quickly) which release exudate forming a characteristic golden/brown crust.
- Once crusts have dried they separate leaving mild erythema which then fades — healing occurs spontaneously without scarring within 2-3 weeks. The course may be more prolonged in people with pre-existing skin conditions (such as eczema or scabies) or in hot/humid climates.
- Lesions can develop anywhere on the body but are most common on exposed skin on the face (in particular the peri-oral and peri-nasal areas), limbs and flexures (such as the axillae). Satellite lesions may develop following autoinoculation.
- Non-bullous impetigo is usually asymptomatic but may be mildly itchy. Systemic features are uncommon but in severe cases regional lymphadenopathy and fever may occur.
- Bullous impetigo
- Lesions appear as flaccid fluid filled vesicles and blisters (often with a diameter of 1-2 cm) which can persist for 2-3 days. Blisters rupture leaving a thin flat yellow/brown crust. Healing usually occurs within 2-3 weeks without scarring.
- Lesions can occur anywhere on the body but are most common on the flexures, face, trunk and limbs. Bullous impetigo may be particularly widespread in infants.
- Systemic features may occur if large areas of skin are affected and include fever, lymphadenopathy, diarrhoea and weakness.
Impetigo is usually a clinical diagnosis and investigations are not needed. Swabs (of exudate from a moist lesion or deroofed blister) for culture and sensitivities should be considered in cases which are persistent despite treatment, recurrent, or widespread. The possibility of meticillin-resistant Staphylococcus aureus (MRSA) should be considered.
Differential diagnosis
- Skin infections and infestations
- Bacterial skin infections such as cellulitis, ecthyma, erysipelas, staphylococcal scalded skin syndrome, and necrotising fasciitis
- Fungal skin infections such as candidiasis, tinea corporis or tinea capitis
- Parasitic infestations such as scabies
- Viral infections such as varicella zoster or herpes simplex
- Non-infective skin conditions
- Dermatitis such as atopic or contact dermatitis
- Insect bites
- Burns and scalds
- Drug reactions
- Other skin disorders such as pemphigus vulgaris, bullous pemphigoid, lupus erythematosus, erythema multiforme and Sweet's Syndrome
Management
- Reassure the person that impetigo usually heals completely without scarring, and that serious complications are rare.
- Advise the person, and their carers if appropriate, about good hygiene measures to aid healing and reduce the spread of impetigo to other areas of the body and to other people.
- Inform the person of Public Health England exclusion recommendations:
- Children and adults should stay away from school and other childcare facilities or work until lesions are healed, dry and crusted over or 48 hours after initiation of antibiotics.
- Food handlers are required by law to inform employers immediately if they have impetigo.
- Ensure optimal treatment of any pre-existing skin conditions such as eczema, head lice, scabies or insect bites
- Advise people with impetigo, and their parents or carers if appropriate, to seek medical help if symptoms worsen rapidly or significantly at any time, or have not improved after completing a course of treatment
- For localised non-bullous impetigo:
- Consider prescribing hydrogen peroxide 1% cream (apply two or three times daily for 5 days) for people who are not systemically unwell or at a high risk of complications.
- If this is unsuitable, prescribe a short course (5 days) of a topical antibiotic, offer fusidic acid 2% (apply three times a day for 5 days), or mupirocin 2% (apply three times a day for 5 days) if fusidic acid resistance is suspected or confirmed.
- For widespread non-bullous impetigo:
- Offer a short course of a topical OR oral antibiotic for people who are are not systemically unwell or at high risk of complications:
- Topical fusidic acid 2% (apply three times daily for 5 days), or mupirocin 2% (three times daily for 5 days) if fusidic acid resistance is suspected or confirmed, OR
- For adults, prescribe oral flucloxacillin (500 mg four times daily for 5 days)
- For children, prescribe oral flucloxacillin for 5 days (62.5–125 mg four times daily for children aged 1 month to 1 year; 125–250 mg four times daily for children aged 2–9 years; 250–500 mg four times daily for children aged 10-17 years)
- Offer a short course of a topical OR oral antibiotic for people who are are not systemically unwell or at high risk of complications:
- For bullous impetigo or impetigo in people who are systemically unwell or at high risk of complications:
- Offer a short course of oral antibiotic for all people with bullous impetigo or impetigo who are systemically unwell or at high risk of complications:
- For adults, prescribe oral flucloxacillin (500 mg four times daily for 5 days)
- For children, prescribe oral flucloxacillin for 5 days (62.5–125 mg four times daily for children aged 1 month to 1 year; 125–250 mg four times daily for children aged 2–9 years; 250–500 mg four times daily for children aged 10-17 years)
- Offer a short course of oral antibiotic for all people with bullous impetigo or impetigo who are systemically unwell or at high risk of complications:
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
