Cellulitis can often be the reflex diagnosis when a patient presents with red leg in primary care. Elderly patients can sometimes end up having repeated courses of antibiotics over years for supposed cellulitis. These are often requested by relatives or care home workers on the basis of a previous diagnosis for similar symptoms, often in both legs – they may have had prolonged or repeated antibiotic courses, which seem to have had little effect. In such cases, further enquiry may reveal that both legs have been red, scaly, sore and itchy for a few days – but the patient is otherwise well, with no fever.
The reality
The red leg – and especially ‘red legs’ – may well be caused by varicose eczema rather than cellulitis. Misdiagnosis all too often leads to unnecessary courses of antibiotics which, because of the lack of response, may become prolonged or repeated. And once the red leg flare-up has settled, and the diagnostic precedent set, this may become a recurring scenario, with whoever reports the relapse – which may be the patient, carer or sometimes nurse – taking the original diagnosis as gospel.
Secondary care studies suggest that cellulitis is misdiagnosed in between 28-33% of cases, and that in 37% of these the true diagnosis is varicose eczema.1,2 These percentages may well be higher in primary care given that community-based cases represent the milder end of the spectrum, and the ‘milder’ the case (for example, with no systemic upset), the more likely the ‘cellulitis’ is, in fact, varicose eczema.
Various authors have drawn attention to this possible diagnostic confusion and suggested ways that the differentials may be distinguished.3,4
How to approach ‘red leg’ presentations
The box below summarises and collates they key distinguishing features highlighted by various authors. Crusting or scaling is cited as the most important discriminator, being an important sign of eczema but absent in cellulitis.4 Bilaterality must also be a significant feature, being relatively common in varicose eczema but described as ‘rare’ in cellulitis.5
| Varicose eczema | Cellulitis |
| May be bilateral | Nearly always unilateral |
| Crusting or scaling | No crusting or scaling |
| Vesicles common | No vesicles (occasionally bullae) |
| No fever/systemic upset | May be fever/systemic upset |
| Onset and progression usually gradual | Onset sudden and progression rapid |
| Itchy | Painful or tender |
| CRP/ESR/WCC normal | CRP/ESR/WCC likely to be elevated |
| Commonly recurs | Occasionally recurs |
Caveats
As always in practice there will be sometimes be unusual or complicated presentations that make it more difficult for us to distinguish between the two conditions. The table highlights that varicose eczema usually starts gradually and progresses slowly. However, it can sometimes start surprisingly abruptly, with acute inflammation and swelling.
And just to add to the confusion, varicose eczema can, of course, become secondarily infected, so the two conditions can co-exist. This is the likely explanation for an apparent cellulitis seeming to respond well initially to antibiotics and then reaching a plateau of improvement which proves resistant to further, or different, antibiotics.
Key points
- Varicose eczema is commonly misdiagnosed as cellulitis
- A variety of features can help distinguish between the two, the most useful being bilaterality and crusting/scaling, which are both suggestive of varicose eczema
- Taking time to figure out the correct diagnosis is likely to reduce inappropriate antibiotic use and ensure the patient receives effective treatment for their varicose eczema (emollients, steroid creams and compression)
- If an apparent cellulitis partially responds to antibiotics, the primary issue may be secondarily infected varicose eczema, which will then need treating in its own right.
Dr Keith Hopcroft is a GP in Basildon, Essex
References
- David C, Chira S, Eells S et al. Diagnostic accuracy in patients admitted to hospital with cellulitis. Dermatol Online J 2011;17(3):1
- Levell N, Wingfield C, Garioch J. 2011. Severe lower limb cellulitis is best diagnosed by dermatologists and managed with shared care between primary and secondary care. Br J Dermatol 164(6):1326-8
- Salmon M. Differentiating between red legs and cellulitis. Independent Nurse. 2016
- Quartey-Papafio C. 1999. Importance of distinguishing between cellulitis and varicose eczema of the leg. BMJ 1999;318:1672
- Batra V, Baras A. Bilateral cellulitis. BMJ Case Reports 2015
