Stevens-Johnson syndrome overview

# Overview
Stevens-Johnson syndrome is a life-threatening condition affecting the skin, in which due to cell death the epidermis separates from the dermis.  The syndrome is thought to be a hypersensitivity complex affecting the skin and the mucous membranes.  Although the majority of cases are idiopathic, the main class of known causes is medications, followed by infections and (rarely) cancers.

# Historical Perspective
It is named for Dr. Albert Mason Stevens and Dr. Frank Chambliss Johnson, American pediatricians who jointly published a description of the disorder in 1922.

# Classification
There is agreement in the medical literature that Stevens-Johnson syndrome can be considered a milder form of toxic epidermal necrolysis (TEN). Stevens-Johnson Syndrome involves less than 10 percent of body surface area while TEN involve more than 30 percent body surface area. However, there is debate whether it falls on a spectrum of disease that includes erythema multiforme and erythema multiforme major (also known as erythema multiforme majus).

# Pathophysiology
SJS, like toxic epidermal necrolysis and erythema multiforme, are characterized by confluent epidermal necrosis with minimal associated inflammation. The acuity is apparent from the (normal) basket weave-like pattern of the stratum corneum. The exact pathogenesis of SJS/TEN is not completely understood. However, It is believed that SJS/TEN is immune mediated and the result of a MHC Class-I restricted T-cell mediated cytotoxic reaction to drug antigens in keratinocytes leading to apoptosis. Drug antigens bind to MHC-I and T cell Receptors (TCR) leading to the clonal proliferation of the drug specific cytotoxic T cells. On the activation of these T cells, various cytotoxic signals, including Fas/Fas ligand , Perforin/Granzyme B , and Granulysin, are known to be responsible for mediating the damages in skin lesions and the subsequent worsening of the disease.

# Causes
Stevens-Johnson Syndrome is caused by drug reactions in the majority of the cases although it is also seen in certain viral and bacterial infections, and certain malignancies. Most commonly implicated drugs include sulfa drugs, Allopurinol, anti-epileptics (phenobarbital, carbamazepine, lamotrigine), antibiotics (for example Penicillin), and NSAIDs. Infections that are associated with SJS may include HIV, HSV, Mumps, Mycoplasma, Mycobacteria, Hepatitis and Streptococcal Infection.

# Risk Factors
Common risk factors in the development of SJS include Immunodeficiency, HIV infection, active malignancy (particularly Hematological cancers), genetic Predisposition ( HLA-B 1502 and HLA-B 5801 variants in particular) on exposure to anti-epileptic medications or Allopurinol. Other risk factors may include past or family history of SJS/TEN, radiation therapy and rapid use of medications.

# Epidemiology and Demographics
SJS is a rare condition, with a reported incidence of around 2-7 per 1000,000 people per year and a mean mortality rate of 4.8 percent. It is seen in patients of all age groups but particularly in children and young adults. Females are more commonly affected than males

# Natural History, Complications and Prognosis
SJS proper (with less than 10% of body surface area involved) has the mortality rate of around 5%. The risk of death can be estimated using the SCORTEN scale, which takes a number of prognostic indicators into account. Other outcomes include organ damage and blindness.

# Diagnosis

## History and Symptoms
Stevens-Johnson syndrome (SJS) usually begins with a fever, sore throat, and fatigue, which is misdiagnosed and usually treated with antibiotics. Ulcers and other lesions begin to appear in the mucous membranes, almost always in the mouth and lips but also in the genital and anal regions. Those in the mouth are usually extremely painful and reduce the patient's ability to eat or drink. Conjunctivitis of the eyes occurs in about 30% of children who develop SJS. A rash of round lesions about an inch across arises on the face, trunk, arms and legs, and soles of the feet, but usually not the scalp.

## Physical Examination
Common physical examination findings of SJS include rash or redness that is seen as red or reddish purple macules that enlarge to form bullae, vesicles and may rupture later to leave denuded skin underneath. Nikolsky sign may be positive which shows sloughing of the skin by gentle lateral pressure on the erythematous skin. In addition to skin, mucosal involvement is found mostly in oral mucosa in addition to the nasopharynx and ocular involvement-can be seen as edema, erythema, blistering, sloughing, necrosis and ulceration. In addition to these changes: fever, hypotension, and tachycardia can be seen in patients with SJS

## Laboratory Findings
SJS is mainly diagnosed through the clinical skin findings. However, a skin biopsy is helpful in making the definitive diagnosis. Other tests are done to either rule out the superimposed bacterial infection, measure disease severity or detect the causative agent or organism. Tests include CBC, BMP, Blood cultures, ESR, CRP, IL-6, ELISA for virus detection among others.

## Chest X-Ray
There are no x-ray findings associated with SJS. However, an x-ray may be helpful in the diagnosis of pulmonary complications of Stevens-Johnson Syndrome, in which CXR may show interstitial lung infiltrates

# Treatment
Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis should be managed in a burn unit, Specialized dermatology or Intensive Care unit. Patient's fluid status, hemodynamic stability, wound surface area and pain should be assessed and managed immediately upon admission. Treatment is initially similar to that of patients with thermal burns, and continued care can only be supportive (e.g. IV fluids) and symptomatic (e.g. analgesic mouth rinse for mouth ulcer); there is no specific drug treatment. Treatment with corticosteroids is controversial since it might aggravate the condition or increase risk of secondary infections. Other agents have been used, including cyclophosphamide and cyclosporine, among with cyclosporin has exhibited some therapeutic success. Intravenous immunoglobulin (IVIG) treatment has shown some promise in reducing the length of the reaction and improving symptoms. Other common supportive measures include the use of topical pain anesthetics and antiseptics, maintaining a warm environment, and intravenous analgesics. An ophthalmologist should be consulted immediately, as SJS frequently causes the formation of scar tissue inside the eyelids leading to corneal vascularization and impaired vision, as well as a host of other ocular problems. Also, an extensive physical therapy program ensues after the patient is discharged from the hospital.