Stevens–Johnson Syndrome

Stevens–Johnson Syndrome (SJS) is a severe skin reaction that falls under the spectrum of febrile mucocutaneous drug reactions, which includes toxic epidermal necrolysis (TEN) and their overlap (SJS/TEN). Though generally less severe than TEN, SJS is a significant dermatological emergency.

Signs and Symptoms

SJS typically begins with non-specific symptoms such as fever, sore throat, and fatigue, often leading to initial misdiagnosis and inappropriate antibiotic treatment. Within a few days, patients may experience painful skin with burning sensations, and mucous membrane lesions start to appear, predominantly in the mouth and lips but also potentially in the genital and anal regions. These mucosal ulcerations are exceedingly painful, impacting the patient's ability to eat or drink. Conjunctivitis is seen in about 30% of paediatric cases. A characteristic rash of round lesions, approximately an inch across, often appears on the face, trunk, arms, legs, and soles of the feet.

Causes

SJS arises from an immune system disorder often triggered by medications or infections, though genetic predispositions play a significant role. Medications are the primary cause, particularly antibiotics like sulfonamides, and other drugs such as lamotrigine, allopurinol, and carbamazepine. Infectious causes include Mycoplasma pneumoniae, cytomegalovirus, and various viral infections.

Pathophysiology

SJS is a type IV hypersensitivity reaction, specifically subtype IVc, in which a drug or its metabolite stimulates cytotoxic T cells and T helper cells to initiate an autoimmune attack on self-tissues. This involves the immune system's antigen presentation pathways, where a drug-related epitope binds to HLA proteins, stimulating T cells to attack tissues. Genetic predispositions, such as specific HLA serotypes, play a very important role in susceptibility to SJS.

Diagnosis

Diagnosis involves assessing the extent of skin involvement, with less than 10% of the skin affected in SJS, 10–30% in SJS/TEN overlap, and over 30% in TEN. A positive Nikolsky's sign and skin biopsy can aid in diagnosis, revealing full-thickness epidermal necrosis with minimal inflammation.

Treatment

Treatment is primarily supportive and typically involves hospitalisation in specialised units like burn or intensive care units. The mainstay of therapy includes stopping the causative drug, providing pain relief, maintaining hydration, and preventing infections. Medications such as corticosteroids and intravenous immunoglobulins have been used with varying success. Ophthalmologic consultation is very important due to the risk of ocular complications, including blindness.

Prognosis

SJS has a mortality rate of around 5%, which increases significantly in TEN. Prognostic indicators are considered using the SCORTEN scale, which helps estimate the risk of death. Early withdrawal of the causative drug improves prognosis. Long-term consequences may include organ damage, ocular morbidities, and restrictive lung disease.

Epidemiology

SJS is rare, with an incidence of 1–2 cases per million people per year, affecting individuals of all ages but more commonly seen in adults. The condition has been recognised since 1922 when it was first described by Stevens and Johnson. Notable cases include celebrities and public figures who have brought attention to this severe condition.

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Self-assessment MCQs (single best answer)

What is the primary cause of Stevens–Johnson Syndrome (SJS)?

Which of the following is a common initial symptom of SJS?

Which symptom is typically observed in about 30% of paediatric SJS cases?

What type of hypersensitivity reaction is SJS classified as?

SJS predominantly affects which areas of the body?

Which diagnostic sign is typically positive in SJS?

What is the typical treatment setting for a patient with SJS?

Which of the following drugs is commonly associated with causing SJS?

What is the mortality rate of Stevens–Johnson Syndrome (SJS)?

What is the SCORTEN scale used for in the context of SJS?