Cellulitis and Erysipelas Flashcards
Define cellulitis.
Cellulitis is an acute spreading infection of the skin with visually indistinct borders that principally involves the dermis and subcutaneous tissue.
It is characterised by erythema, oedema, warmth, and tenderness, and commonly occurs in an extremity.
Define erysipelas.
Erysipelas is a distinct form of superficial cellulitis with notable lymphatic involvement and is raised, sharply demarcating it from uninvolved skin.
How common is cellulitis?
0.4% of hospital admissions
some forms of cellulitis are unique to women
What is the aetiology of cellulitis?
Disruptions in the cutaneous barrier –> entry of micro-organisms to the dermal and subcutaneous tissues
Beta -haemolytic streptococci and staphylococcus aureus are the most common organisms.
MRSA is not uncommon.
If occurring in the orbit, Haemophilus influenzae is the most common cause. The infection
often arises from adjacent sinuses.
What are the risk factors for cellulitis?
- Prior episode of cellulitis - probably due to persistance of other risk factors.
- Ulcer/wound
- Dermatosis
- Tinea pedis interdigitalis - disruption of cutaneous barrier allows micro-organism entry into tissue.
- Lymphoedema
- Venous insufficiency/chronic leg oedema - Cellulitis following saphenous venectomy is a well-recognised association. Chronic oedema may also contribute to risk - thought that stasis of fluid reduced local host defences, leading to infection.
- Overweight -
Other:
- Bite (human/dog/cat)
- Fresh water exposure
- Salt water exposure
- Diabetic foot ulcer
What are the signs and symptoms of cellulitis?
- Skin discomfort
- Macular erythema with indistinct borders on the skin - cellulitis
- Shiny, smooth skin
- Not normally itchy
- Disruption of cutaneous barrier
- Erysipelas - raised erythema with clearly demarcated margins. Less serious than cellulitis.
- Possible fever, malaise
Other:
- Lesion: erythema, oedema, warm tender indistinct margins. Pyrexia may signify systemic spread.
- Exclude abscess: Test for fluid thrill or fluctuation. Aspirate if pus suspected.
- Periorbital: Swollen eyelids. Conjunctival injection.
- Orbital cellulitis: Proptosis, impaired acuity and eye movement. Test for relative afferent pupillary defect, visual acuity and colour vision (to monitor optic nerve function).
What is the main difference between cellulitis and erysipelas?
Erysipelas is more superficial. It may also be well demarcated.
Cellulitis affects deeper tissues.This is a more serious infection. However, it may not always be possible to distinguish between the two .
What are the most common locations for cellulitis?
- Mostly starts on lower leg around ankle
- Periorbital cellulitis occurs on around the eyelids
- Erysipelas is more common on the face than cellulitis
- Sometimes sinusitis cab spread to the eye causing orbital cellulitis
- Leaning on the elbow too much can lead to olecranon bursitis
What conditions can be mistaken for cellulitis? What differentiates them? (2)
- Insect bites can have surrounding redness which is usually only a histamine reaction and goes away in a few days. Insect bites are itchy but cellulitis isn’t. Cellulitis also takes more time to develop (not overnight).
- Varicose eczema - redness on legs of elderly; usually occurs on both legs unlike cellulitis. It also isn’t painful unlike cellulitis.
Correct diagnosis is important as it prevents taking antibiotics for no reason.
What investigations should you do for cellulitis?
Usually clinical diagnosis - history and examination.
Other:
FBC - raised WCC
Purulent focus culture and molecular diagnostic procedures - growth of typical pathogen (e.g. Staph aureus). Done if cellulitis is associated with a wound or purulent focus.
MRI/CT - in orbital cellulitis to assess posterior spread
How do you treat cellulitis?
Medical: Oral penicillins (e.g. flucloxacillin, benzylpenicillin, coamoxiclav) or tetracyclines are
effective in most community-acquired cases. In the hospital, treat empirically using local
microbiological guidelines but change depending on sensitivity of any cultured organisms.
Intravenous use may be necessary.
Surgical: Orbital decompression may be necessary in orbital cellulitis. This is an emergency.
Abscess: Abscesses can be aspirated, incised and drained or excised completely.
What are the complications of cellulitis?
- Sepsis
- In orbital cellulitis, there may be permanent vision loss and spread to brain, abscess formation, meningitis, cavernous sinus thrombosis.
- Damage to lymphatics –> chronic oedema
- Localised tissue damage
- Sloughing of overlying skin
What is the prognosis with cellulitis?
Excellent - resolves with therapy
Recurrence may occur
What is the most to least likely diagnosis and why?
(ruptured Baker’s cyst, ischaemic leg, DVT, urticarial reaction, cellulitis)
- Cellulitis - red, swollen, tender leg and a pyrexia so most likely. Usually well demarcated and warm to palpation
- DVT- possible with fever but must ask RFs
- Ischaemic leg
- Ruptured Bakers cyst - would be very acute onset and at the back of the knee (often associated with OA of the knee joint)
- Urticarial reaction - does not present in this manner
What are the two most common organisms causing skin and soft tissue infections?
- Streptococcus pyogenes (also known as Group A Streptococcus)
- Staphylococcus aureus.
Other:
- Strep viridans = oral cavity as commensal
- Staph epidermidis = coagulase negative staph living on skin as harmless commensal
- Enterococcus faecalis = gut flora
All can cause disease when in the wrong place or with assistance.
