Question 25.1

a) What is this skin rash?

b) Give three causes

c) Apart from the skin, what other tissues are involved?

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College Answer

a) What is this skin rash?
•    Erythema multiforme

b) Give three causes
•    Herpes simplex infection
•    Mycoplasma pneumonia
•    Streptococcal infections
•     Drugs
•     SLE
•     Leukaemia

c) Apart from the skin, what other tissues are involved?
•    Mucous membranes, especially oral mucosa


That is a nice shot of erythema multiforme from Wikipedia.

How does one recognise it? Apparently, the lesions are typical. This is a disease of the skin and mucous membranes.

Approximately 50% of cases are associated with herpes simplex.

The rest of the causes can be classified as either infectious or drug-related:

Infectious causes:

  • Mycoplasma pneumoniae
  • Fungal infections eg. candida

Drugs which cause erythema multiforme:

  • Phenytoin
  • Barbiturates
  • NSAIDs
  • Penicillins
  • Phenothiazines
  • Sulfonamides


Clark Huff, J., William L. Weston, and Marciih G. Tonnesen. "Erythema multiforme: a critical review of characteristics, diagnostic criteria, and causes."Journal of the American Academy of Dermatology 8.6 (1983): 763-775.

Leaute-Labreze, C., et al. "Diagnosis, classification, and management of erythema multiforme and Stevens–Johnson syndrome." Archives of disease in childhood 83.4 (2000): 347-352.