Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis

Stevens-Johnson syndrome and toxic epidermal necrolysis (also known as Lyell's syndrome) are two similar diseases that occur due to a serious immune reaction, usually after the use of certain medications. Both are a kind of severe allergic reaction.

Stevens-Johnson syndrome and toxic epidermal necrolysis
Stevens-Johnson syndrome and toxic epidermal necrolysis

What is it?

Stevens-Johnson syndrome and toxic epidermal necrolysis are idiosyncratic reactions, that is, they occur rarely, acutely and unpredictably. They are not exactly a side effect of the drug because the reaction is unpredictable and occurs not because of a specific drug problem but because of a characteristic of the individual's immune system. Stevens-Johnson syndrome and toxic epidermal necrolysis occur in approximately 1 in 1 million people.

Both Stevens-Johnson syndrome and toxic epidermal necrolysis are reactions that usually involve the skin and mucous membranes. These reactions are characterized by fever and rashes, which can lead to necrosis and extensive detachment of the most superficial layer of the skin (we will explain the symptoms in more detail below).

Stevens-Johnson syndrome and toxic epidermal necrolysis are a medical emergency and should be treated in a hospital setting.


Stevens-Johnson syndrome and toxic epidermal necrolysis are distinguished by the severity and percentage of body surface area affected.

Stevens-Johnson syndrome is the least severe form, with skin peeling limited to less than 10% of body surface area.

Toxic epidermal necrolysis, or Lyell's syndrome, is the most severe form of the disease, involving more than 30% of the body surface area. The longer the involvement of the skin, the greater the risk of complications and death.

The mucous membranes are affected almost 100% in both cases, usually in two or more distinct sites at the same time, such as mucosa of the eyes, mouth, airways or genitals.

Stevens-Johnson syndrome has a mortality of about 3% while in toxic epidermal necrolysis the mortality reaches 30% of the cases.


In the vast majority of cases, Stevens-Johnson syndrome and toxic epidermal necrolysis are triggered by some medication. In children, medicines are also the main cause, but it is not uncommon for the trigger to be an infection.

Rarely both reactions can be triggered by contact with chemicals, vaccination, existence of tumors, consumption of natural herbs or foods.

More than 200 drugs have been described as possible triggers for both diseases, but most cases occur after the use of one of the following drugs:
  • Valproic acid
  • Allopurinol
  • Amitiozone
  • Amoxicillin
  • Ampicillin
  • Barbiturates
  • Carbamazepine
  • Phenylbutazone
  • Phenobarbital
  • Hydantoin
  • Lamotrigine
  • Nevirapine
  • Piroxicam
  • Sulfadiazine
  • Sulfadoxine
  • Sulfasalazine
  • Trimethoprim-sulfamethoxazole (cotrimoxazole)

In the case of infections, pneumonia caused by Mycoplasma pneumonia seems to be one of the most common causes. Other possible infections to trigger a syndrome of Stevens-Johnson syndrome or toxic epidermal necrolysis are:

It is important to point out once again that both reactions are very rare. Only 1 in 1 million people will develop a Stevens-Johnson type reaction to one of these drugs or infections.


In cases caused by drugs, which are the majority, symptoms usually begin between 1 and 3 weeks after exposure to the drug.

The picture begins with a nonspecific infection, and may appear as an initial picture of the flu, with fever, sore throat, coughing and burning or itching of the eyes. About 3 days later the first lesions on the skin appear.

Skin lesions usually begin as erythematous macules (translating: reddish spots). In Stevens-Johnson the maculae are more rounded, and the central region may be purplier. In toxic epidermal necrolysis the males are more diffuse, atypical and with less demarcated borders.

In both diseases, the macules can be very painful. The lesions are usually distributed symmetrically, starting on the face and chest before spreading to other areas. The scalp is typically spared.

Macules develop into blisters. Within a few days, the skin begins to undergo necrosis, loosening and peeling. The peeling progresses rapidly for two to three days and then stabilizes. In toxic epidermal necrolysis, there may be fulminant cases, in which 100% of the epidermis is removed in a matter of hours.

Mucoses are involved in more than 90% of cases of Stevens-Johnson syndrome and toxic epidermal necrolysis. Typically, at least two mucous membranes are affected at the same time. Crust and painful ulcers can occur on any mucosal surface such as eyes, mouths, larynx, pharynx and genitals.

In more severe cases, internal organs can be affected, such as heart, lung, kidneys and liver. Eye damage can lead to blindness. When it does not, it usually leaves some sort of sequel in sight.

The disease usually lasts two to four weeks. The skin takes more or less this same time to grow again, however, scars, bumps and irregularities can be permanent. Hair and nails may also grow irregularly in the affected areas.

The longer the lesions on the skin and mucosa, the greater the risk of death, as the patient becomes very susceptible to opportunistic infections and sepsis, Since skin is our main protection against environmental germs.


The first step is to remove the causative agent of the disease. Any new remedy should be immediately suspended. The earlier the drug is discontinued, the better the prognosis.

The patient with Stevens-Johnson syndrome and, mainly, toxic epidermal necrolysis should be treated as if it were someone who suffered extensive and severe burns. Some hospitals have areas to treat large burnings. It is in these sectors that the patient should be hospitalized.

The treatment is supportive, consisting in keeping the patient alive while the skin does not recover and the extensive inflammatory reaction does not disappear. The patient should always be well hydrated with serum (absence of skin causes severe dehydration) and all skin and mucosal wounds should be carefully treated, if necessary, with surgical removal of necrotic areas.

The use of corticosteroids is still controversial, but can be used if the reaction is detected in early stages.

The drug that triggered Stevens-Johnson syndrome or toxic epidermal necrolysis can never be used in these patients.

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