Erythema Multiforme - Causes

Causes

See also: List of human leukocyte antigen alleles associated with cutaneous conditions

Many suspected aetiologic factors have been reported to cause EM.

• Infections: Bacterial (including Bacillus Calmette-Guérin (BCG) vaccination, haemolytic Streptococci, legionellosis, leprosy, Neisseria meningitidis, Mycobacterium, Pneumococcus, Salmonella species, Staphylococcus species, Mycoplasma pneumoniae), Chlamydial.
• Fungal
• Parasitic (Trichomonas species, Toxoplasma gondii),
• Viral (especially Herpes simplex).
• Drug reactions, most commonly to: Antibiotics (including, sulphonamides, penicillin), anticonvulsants (phenytoin, barbiturates), aspirin, antituberculoids, and allopurinol and many others.
• Physical factors - Radiotherapy, cold, sunlight
• Others - Collagen diseases, vasculitides, non-Hodgkin lymphoma, leukaemia, multiple myeloma, myeloid metaplasia, polycythemia

EM minor is regarded as being triggered by HSV in nearly 100% of cases. A herpetic aetiology also accounts for 55% of cases of EM major. Among the other infections, Mycoplasma infection appears to be a common cause.

Herpes simplex virus suppression and even prophylaxis (with acyclovir) has been shown to prevent recurrent erythema multiforme eruption. The human form of orf can also cause erythema multiforme.