Red flag symptoms: Erythema

Dr Tillmann Jacobi highlights possible causes for concern with this common presentation.

  • Non-blanching in an unwell patient
  • Marked systemic upset
  • Spreading from broken skin (e.g. venous leg ulcers)
  • Respiratory features
  • Recent tick bite (especially if in a known geographical risk area)
  • Pregnancy

Erythema means an area of localised or generalised blanching redness of the skin due to vasodilation. It can be caused by mechanical or physical skin injury (including radiation), infection or inflammation.

Reasons for acute or chronic/recurrent erythema range from obvious and simple situations, such as localised urticarial reaction after an insect bite, through moderate significance (e.g. burns at varying degrees) to potentially life-threatening situations such as anaphylaxis.

Up to 50 per cent of occurrences have no apparent medical cause.

Possible causes
  • Urticaria
  • Lyme disease
  • Liver disease
  • Erythema infectiosum
  • Erythema multiforme

Lyme disease
Erythema migrans develops as part of Lyme disease after infection with Borellia burgdorferi. The incubation period may be 3-30 days after a bite or possibly after the inappropriate removal of an infective tick.

One large single lesion (up to 60cm diameter) often located on the limbs, might be accompanied by others elsewhere. The red flag is the presence of additional intermittent flu-like symptoms.

Beware of the risk of potentially significant systemic complications. Considering Lyme disease as a differential diagnosis is important, as well as prompt management in at-risk cases with serology and antibiotic treatment according to local guidelines.

Erythema migrans after a bite (Photograph: Adam Hart-Davis/SPL)

Erythema infectiosum
Erythema infectiosum is also known as Fifth disease or 'slapped cheek syndrome'. It is caused by the human erythrovirus or parvovirus. It typically affects children at school-age, and the majority of adults will have acquired immunity.

A bright looking rash starts on the face and spreads over the limbs, but often spares the palms and soles. There is rarely significant systemic upset and the condition resolves within a week.

Exposure of pregnant women without immunity to the virus can be problematic: although the chances are small, an infection can lead to an increased risk of miscarriage, fetal death (up to 10 per cent), or chronic infection-related conditions, especially in the first 20 weeks of pregnancy.

Suspected cases should have a parvovirus serology and a possible referral for close ultrasound monitoring of the fetal growth.

Erythema multiforme
'Target lesions' in cases of erythema multiforme can develop as a reaction to medications (NSAIDs), infections or inflammatory conditions. These may last for several weeks. The major, potentially life-threatening complication Stevens-Johnson syndrome is rare. Relevant differential diagnoses including pemphigoid, pemphigus and dermatitis herpetiformis need to be considered.

If the patient is well, treating the underlying cause and symptomatic relief with antihistamines and topical steroids might be all that is needed.

Palmar erythema is a reddening of the palms of the hands, sometimes the soles of the feet. It can be a feature of chronic liver disease, pregnancy, thyrotoxicosis, rheumatoid arthritis or polycythaemia. It may also be idiopathic.

  • Dr Jacobi is a salaried GP in York

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