Dermatology: Impetigo Flashcards
What is the definition of impetigo [1]
What are the most likely pathogens causing impetigo? [1]
What are the two classifications? [1]
Impetigo is a superficial bacterial skin infection, usually caused by the staphylococcus aureus bacteria. A “golden crust” is characteristic of a staphylococcus skin infection.
It is also less commonly caused by the streptococcus pyogenes bacteria. Impetigo is contagious and children should be kept off school during the infection.
Impetigo can be classified as non-bullous or bullous.
Describe the difference between bullous and non-bullous impetigo:
- location
- characteristics
- treatment
Non-Bullous Impetigo
- occurs around the nose or mouth.
- the exudate from the lesions dries to form a “golden crust”. They are often unsightly but do not usually cause systemic symptoms or make the person unwell.
- Topical fusidic acid can be used to treat localised non-bullous impetigo. Draft NICE guidelines from August 2019 suggest using antiseptic cream (hydrogen peroxide 1% cream) first line rather than antibiotics for localised non-bullous impetigo.
- Oral flucloxacillin is used to treat more wide spread or severe impetigo.
Bullous Impetigo
- Bullous impetigo is always caused by the staphylococcus aureus bacteria. These bacteria can produce epidermolytic toxins that break down the proteins that hold skin cells together. This causes 1 – 2 cm fluid filled vesicles to form on the skin. These vesicles grow in size and then burst, forming a “golden crust”. Eventually they heal without scarring. These lesions can be painful and itchy.
- This type of impetigo is more common in neonates and children under 2 years, however it can occur in older children and adults.
- It is more common for patients to have systemic symptoms. They may be feverish and generally unwell.
- Treatment of bullous impetigo is with antibiotics, usually flucloxacillin. This may be given orally or intravenously if they are very unwell or at risk of complications.
Which organisms are most likely to cause cellulitis in children? [2]
Staph aureus or GAS (Streptococcus pyogenes)
How do you treat cellulitis? [+]
Eron Class I
* oral antibiotics (co-amox)
* oral flucloxacillin as first-line treatment for mild/moderate cellulitis
* oral clarithromycin, erythromycin (in pregnancy) or doxycycline is recommended in patients allergic to penicillin.
Eron Class II
* NICE recommend: ‘Admission may not be necessary if the facilities and expertise are available in the community to give intravenous antibiotics and monitor the person - check local guidelines.’
Eron Class III-IV
* admit
* NICE recommend: oral/IV co-amoxiclav, oral/IV clindamycin, IV cefuroxime or IV ceftriaxone
Name four symptoms of periorbital cellulitis [4]
Swelling, fever
Proptosis: one or both of eyes bulge from their natural position
Opthalmoplesia: paralysis of eye muscles
Colour vision disruption
If a child has orbital involvement - what investigations would you perform? [1]
CT scan
What is the difference between orbital and periorbital cellulitis? [2]
Periorbital cellulitis:
- also known as preseptal cellulitis, affects the eyelid and surrounding skin anterior to the orbital septum
- secondary to local trauma, sinusitis or upper respiratory tract infections.
Orbital cellulitis
- is a post-septal infection involving the orbit’s soft tissues posterior to the orbital septum
Describe the presentation of periorbital cellulitis [+]
- Red, swollen, painful eye of acute onset
- Fever
- Partial or complete ptosis of the eye due to swelling
- Orbital signs (pain on movement of the eye, restriction of eye movements, proptosis, visual disturbance, chemosis, RAPD) must be ABSENT in preseptal cellulitis - their presence would indicate orbital cellulitis
How do you investigate for preseptal cellulitis? [3]
Investigations
* Bloods - raised inflammatory markers
* Swab of any discharge present
* Contrast CT of the orbit may help to differentiate between preseptal and orbital cellulitis. It should be performed in all patients suspected to have orbital cellulitis
Management of preseptal cellulitis? [4]
Mild-moderate:
- Co-amoxiclav oral
- patients allergic to penicillins, clarithromycin or erythromycin can be used.
Severe:
- IV Ceftriaxone or cefotaxime
- In the presence of methicillin-resistant Staphylococcus aureus (MRSA) risk factors, vancomycin or teicoplanin should be added.
Surgical Intervention:
- Although rare, surgical intervention may be required in the case of an abscess formation that does not respond to medical management alone.
If periorbital cellulitis doesn’t improve after 48 hours of treatment - what alternative dx should you suspect? [1]
Clinical improvement should be seen within 48 hours of initiating appropriate antibiotic therapy. If no improvement is observed, reassess the patient and consider alternative diagnoses such as orbital cellulitis.
Define what is meant by orbital cellulitis [1]
Where does the infection most commonly come from in the body? [1]
Orbital cellulitis is the result of an infection affecting the fat and muscles posterior to the orbital septukm, within the orbit but not involving the globe. It is usually caused by a spreading upper respiratory tract infection from the sinuses and carries a high mortality rate
The clinical features of orbital cellulitis are grouped into five classic signs, collectively known as the ‘5 P’s’.
Describe the 5 Ps [5]
Pain:
- Pain is a prominent feature of orbital cellulitis and is usually described as throbbing or a deep ache.
- The pain often intensifies with eye movements and can radiate to the forehead, cheek, or teeth.
Proptosis (Exophthalmos):
- This refers to a forward displacement or protrusion of the eyeball.
- It is due to inflammation and oedema of the orbital contents, or in severe cases, formation of an abscess.
- Proptosis can be assessed clinically by lateral inspection or measured with an exophthalmometer.
Periocular Swelling (Oedema):
- Periocular swelling and redness result from the inflammatory response within the orbital tissues.
- The patient may present with swollen eyelids, chemosis (swelling of the conjunctiva), and erythema. It’s crucial to distinguish this sign from preseptal cellulitis, which affects only the eyelid and periorbital tissues, without the involvement of the orbital contents.
Pupil Involvement and Visual Changes:
- This may present as blurred vision, decreased visual acuity, diplopia (double vision), or even loss of vision in severe, advanced cases.
- A relative afferent pupillary defect (RAPD) may be present, indicating optic nerve involvement. These features necessitate urgent attention, given the risk of permanent vision loss.
Palsy (Ophthalmoplegia):
- Due to the inflammation and swelling in the orbit, there can be restriction or paralysis of the extraocular muscles, leading to impaired eye movements (ophthalmoplegia). This can further contribute to the complaint of diplopia.
Which imaging modality would you get for orbital cellulitis? [1]
What would it show? [2]
CT with contrast - Inflammation of the orbital tissues deep to the septum, sinusitis.
How would you manage orbital cellulitis? [1]
Management
admission to hospital for IV antibiotics
