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In this lecture, we're going to talk about Erythema Multiforme and Stevens-Johnson Syndrome.
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So, erythema multiforme is a hypersensitivity reaction. It usually happens to infections such as
HSV or mycoplasma or just viral illness. Rarely, it can be a drug reaction or it can be from
cancer, collagen vascular disease or it may be idiopathic and people just don't know what's
causing it. The lesions may be vesicular or bullous but usually they're targetoid lesions with a
central papule surrounded by an erythematous ring usually around 1 to 3 cm. This is a
particularly severe case right here, you can see. Generally, they'll have a keratinocyte injury
and you can see some necrotic keratinocyte here with a lymphocytic infiltration and on the
skin you can see a sort of central area where it's very red on a milder erythematous base. So
let's go through the causes of E. multiforme, certainly infections. HSV and mycoplasma are
most common but also could be from coccidioidomycosis or histoplasmosis or typhoid or even
rarely leprosy. Drugs can also cause this and we usually think of sulfas and penicillins but
but there are other drugs such as barbiturates, NSAIDs, or any anti-malarials that can also
cause this reaction. Likewise, diseases can cause this such as cancer or lupus or dermatomyositis
or polyarteritis nodosa, basically diseases with a lot of antibodies. The treatment for erythema
multiforme is largely supportive. It maybe itchy and we give antihistamines but generally this
rash is self-limited and will gradually go away on its own, maybe in a week or two. There is a more
severe form of this problem, which is Stevens-Johnson syndrome. In Stevens-Johnson
syndrome, patients develop severe bullous form of erythema multiforme with widespread
mucous membrane involvement and skin involvement and it can be life threatening. It's caused
by generally, again, drug sensitivity or infection and it's immune-mediated, often about 1 to 3
weeks after the exposure. The morbidity and mortality in Stevens-Johnson syndrome is
generally from dehydration or superficial infection of the sloughed skin. It can also be from
toxemia or renal damage and the rate of mortality is low but reasonable, around 1 to 3%. So,
let's talk about what this presents like. Patients often have a prodrome of fever, malaise, or
URI symptoms. They are prodrome to the illness. Then they develop the rash. This can involve
and must involve for diagnosis at least 2 mucous membranes. They can have severe ulceration
of the mouth or they can have significant involvement of the conjunctivitis, corneal ulceration,
or even uveitis. They may also have genital involvement. Patients generally develop very
severe skin disease and they can form bullae which can then slough off and create denuded
skin which can be the source of both infection and dehydration. Here's an example of very
severe keratinocyte apoptosis and epidermal detachment, so you can see the epidermis can
just lift right off. So, to make the diagnosis we generally want to see the typical lesions of
targetoid or atypical skin lesions and involvement of at least 2 mucous membranes. One sign
of Stevens-Johnson syndrome that might show up is Nikolsky's sign. Nikolsky's sign is when you
press down in 1 area adjacent to a bullae and it actually lifts the skin away in the affected
area. So this is a sort of like press next to it and the skin sloughs off. That's classic for
Stevens-Johnson syndrome. When we're worried about patients, we want to calculate the
percent of epidermal detachment. This is treated similarly to burns. If a patient has less than
10% of body surface area involved, we call that Stevens-Johnson syndrome. If it's more than
30%, it is life threatening and we call that toxic epidermal necrolysis. So how do we manage
Stevens-Johnson syndrome? We want to remove the offending agent. If it's a medication, we're
going to stop it. If it's mycoplasma, we might treat it. We want to provide supportive care such
as wound management. These patients do better often in a place that has experience with
burns. We need to provide adequate fluid and sometimes fluid hydration is very important in
these patients because the skin is denuded and they have a lot of insensible losses and since
this condition can take a long time to get better, we need to provide nutrition as well. We need
to provide adequate pain management because these patients are in a lot of pain and in particular
we want to get the ophthalmologist involved because eye care is critical to prevent any future
vision deficit. Lastly, we may try potential adjunctive therapies. Steroids typically do not work.
05:30
People sometimes will try IVIG to try and mitigate somewhat the autoimmune nature of this
disease. So that's a quick summary of E. Multiforme and Stevens-Johnson Syndrome. Thanks for
your attention.