erythema_multiforme
Table of Contents
erythema multiforme
see also:
Introduction
- an uncommon non-contagious acute skin disorder possibly mediated by IgM complexes following infections (far majority are related to Herpes simplex virus (HSV)) or drug exposures.
- peak incidence in the second and third decades of life
- usually occurs in adults 20 to 40 years of age, although it can occur in patients of all ages
- first described by von Hebra in 1860.
Clinical features
- many have a prodrome of fatigue, malaise, myalgia, arthralgias, or fever which may be the precipitant rather than the effect.
- the presence of a cough or SOB raises the likelihood of Mycoplasma pneumoniae-induced rash and mucositis (MIRM) rather than EM, esp. in children.
- most commonly presents with a rash similar to urticaria but with characteristic target lesions especially on the palms
- usually symmetrical with a preference for extensor surfaces and usually on the distal extremities and progress proximally.
- lesions on the dorsal surfaces of the hands and extensor aspects of the extremities are most characteristic however, the alms and soles may also be involved
- the trunk is often spared, but the face and ears may be involved
- may be painful, pruritic, or swollen
- lesions initially start as numerous sharply demarcated red or pink macules that then become round erythematous papules which later develop into target lesions
- The papules may enlarge gradually into plaques several centimeters in diameter.
- The central portion of the papules or plaques gradually becomes darker red, brown, dusky, or purpuric.
- crusting or blistering sometimes occurs in the center of the lesions.
- the characteristic “target” or “iris” lesion has a regular round shape and three concentric zones: a central dusky or darker red area, a paler pink or oedematous zone, and a peripheral red ring.
- target lesions may not be apparent until several days after the onset when lesions of various clinical morphology usually are present
- atypical lesions are raised with poorly defined borders and/or fewer zones of colour variation.
- the “major” form may also include lesions on mucosa (esp. oral and including the tongue)
- lesions generally resolve within 7-10 days and symptoms within 4 weeks (6wks if severe)
- hyperpigmentation may persist for several months
- some will develop a chronic form whereby target lesions develop in response to a local physical stimulus such as a scratch and this lesion may last weeks or months
- ocular involvement can lead to more serious complications including:
- keratitis, uveitis, conjunctival scarring, permanent visual impairment
DDx
- fixed drug reaction
- urticarial vasculitis in adults
- urticarial multiforme in children 1)
- serum sickness
- Mycoplasma pneumoniae-induced rash and mucositis (MIRM) - see mycoplasma
- polymorphous light eruption
- Rowell syndrome (erythema multiforme-like lesions in systemic lupus erythematosus (SLE))
- target lesions with dusky or purpuric centers may resemble pityriasis rosea, lupus erythematosus, vasculitis, or figurate erythema
- patients with bullous lesions should have auto-immune bulous conditions excluded such as:
-
- usually develops within the first week of antibiotic therapy but up to 2 months after starting an anticonvulsant.
- before the rash appears, there is usually a prodromal illness of several days duration resembling an upper respiratory tract infection or 'flu-like illness often with fevers, sore throat, cough, sore eyes, myalgias.
- an abrupt onset of a tender/painful red skin rash starting on the trunk and extending rapidly over hours to days onto the face and limbs (but rarely affecting the scalp, palms or soles), the maximum extent is usually reached by four days.
- the cutaneous involvement differs from EM by involving a greater proportion of the skin, the absence of typical targets and the predominantly axial disposition. The target-like lesions are asymmetrical and made of two concentric zones and purpuric evolution.
- flaccid blisters form and then merge to form sheets of skin detachment, exposing red, oozing dermis. The Nikolsky sign is positive.
- mucosal involvement is prominent and severe, although not forming actual blisters
- the patient becomes very ill, extremely anxious and in considerable pain. In addition to skin/mucosal involvement, other organs may be affected including liver, kidneys, lungs, bone marrow and joints.
- bullous pemphigoid
- paraneoplastic pemphigus
-
Presumed precipitants
- viruses:
- esp. HSV (?90% of cases)
- HSV lesions generally precede EM by 7-10days athough some EM may be due to asymptomatic HSV outbreaks
- It is a delayed HS reaction with the disease beginning with the transport of viral DNA fragments to distant skin sites by peripheral blood mononuclear cells. HSV genes within DNA fragments are expressed on keratinocytes, leading to the recruitment of HSV-specific CD4+ TH1 cells (helper T cells involved in cell-mediated immunity). The CD4+ cells respond to viral antigens with production of interferon-γ, initiating an inflammatory cascade.2)
- bacterial infections such as:
- BCG vaccination, haemolytic strept, legionella, leprosy, N. meningitidis, mycobacteria, pneumococcus, salmonella, staph, chlamydia (mycoplasma rash now have their own enity - see DDx below)
- fungi such as Coccidioides immitis
- parasites such as trichomonas, toxoplasma
- drugs such as antibiotics, anticonvulsants, aspirin, allopurinols, and others
- mechanism is probably via TNF rather than interferon-γ
- vaccines (diphtheria-tetanus, hep B, smallpox)
- physical factors such as radiotherapy, sunlight, cold
- other conditions such as:
Mx
- supportive care
- consider search for causal agent as above if not evident
- treat underlying cause although Rx of Herpes simplex virus (HSV) does not significantly alter the course
- for those with recurrent disease, at least 6 months of continuous oral antiviral therapy (typically acyclovir/aciclovir) 3)
erythema_multiforme.txt · Last modified: 2022/07/11 09:26 by gary1