Stevens-Johnson Syndrome: Drug-Induced Severe Cutaneous Reaction with Medical Emergency Management

Definition and Overview

Stevens-Johnson Syndrome (SJS) is a rare, severe systemic drug reaction characterized by extensive epidermal necrosis and detachment affecting <10% of body surface area (BSA), with mucous membrane involvement in >90% of cases. It represents the clinical spectrum between drug-induced maculopapular exanthem and toxic epidermal necrolysis (TEN), which affects >30% BSA. SJS is a Type IV hypersensitivity reaction (drug-specific T cells) to medications, typically manifesting 1-8 weeks after drug initiation, though reactions can occur from first exposure if prior sensitization exists. The condition constitutes a medical emergency with mortality of 1-5%, with deaths resulting from sepsis, multiorgan failure, and complications from extensive epidermal loss. Prompt recognition and drug discontinuation are life-saving.

Epidemiology

Annual incidence of SJS is 1-2 cases per million persons in developed countries, with incidence increasing to 5-10 per million in areas with higher antiretroviral drug use (HIV-endemic regions). Prevalence is age-independent, affecting all age groups from infants to elderly. Female predominance varies by literature source but is generally slight (ratio 1:1 to 1.5:1). Certain genetic factors increase risk: HLA-B*5701 in abacavir-induced reactions, HLA-A*31:01 in carbamazepine reactions (50% of HLA-A*31:01+ individuals exposed to carbamazepine will develop serious cutaneous adverse reactions including SJS/TEN). Prior history of serious drug reaction increases recurrence risk by 25-100 fold if re-exposed to the same drug or chemically similar drugs.

Causative Medications

High-risk drugs (highest association with SJS/TEN):

• Allopurinol: Historically most common cause in North America; risk 1 per 1,000 exposures (highest of any drug)
• Carbamazepine: Risk 10-20 per 10,000 exposures; associated with HLA-A*31:01
• Sulfonamides: (Trimethoprim-sulfamethoxazole, especially in HIV+ patients) Risk 5-50 per 10,000; now less common due to prophylaxis changes
• NSAIDs: (Naproxen, ibuprofen, others) Risk varies by drug, estimated 1-4 per 10,000
• Phenytoin: Risk 10-20 per 10,000; cross-reactivity with carbamazepine in 20-80% of cases
• Antiretrovirals: (Abacavir, nevirapine) Risk 1-4 per 1,000 in resource-limited settings
• Antimalarials: (Sulfadoxine-pyrimethamine) Risk varies by population, highest in Africa

Moderate-risk drugs: Acetaminophen, barbiturates, methotrexate, oral contraceptives, penicillins (cross-reactivity with cephalosporins <2%), vancomycin, sulindac, piroxicam, codeine

Pathophysiology

SJS results from Type IV cytotoxic T-cell mediated hypersensitivity directed at drug-modified keratinocytes. The mechanism involves: (1) Drug metabolism by keratinocyte or hepatic cytochrome P450 enzymes creating reactive drug metabolites (or the parent drug acts as a hapten); (2) Drug-protein conjugates present via MHC-I on keratinocyte surface to CD8+ T cells; (3) Activation and expansion of drug-specific CD8+ T cells producing granule-mediated cytotoxins (perforin, granzyme B) and TNF-α; (4) Massive keratinocyte apoptosis leading to epidermal necrosis and detachment.

Genetic factors, particularly HLA variants, determine susceptibility. HLA-B*5701 is strongly associated with abacavir reactions (predicts 50-100% of cases). HLA-A*31:01 is associated with carbamazepine reactions (predicts 50-80% of cases). Other HLA associations include HLA-A*02:01 and HLA-B*1502 (phenytoin, carbamazepine in Asian populations).

The cytokine profile shows elevated TNF-α, IFN-γ, IL-15, and granzyme B levels correlating with disease severity and extent. The rapid progression from mild rash to extensive epidermal necrosis (days) suggests highly activated T cell responses.

Clinical Presentation

Prodromal phase (1-3 days): Non-specific symptoms precede skin findings in 50% of cases: fever (38-39°C), malaise, sore throat, arthralgia/myalgia, and conjunctival injection. May be misdiagnosed as viral infection.

Cutaneous phase (days 3-7):

• Timing: Appears 1-8 weeks after drug initiation (median 2-3 weeks)
• Initial morphology: Small, sometimes targetoid or atypical lesions (erythematous macules and papules) with variable appearance
• Rapid progression: Lesions rapidly coalesce and spread over 24-48 hours to trunk and proximal extremities
• Characteristic target lesions: True (concentric) target lesions are rare in drug-induced SJS (<10%); atypical targets (erythematous macule with dusky center and surrounding erythema) are more common. Do NOT rely on classic target lesions for diagnosis.
• Extent: <10% BSA involvement defines SJS; 10-30% BSA = overlap SJS/TEN; >30% = TEN
• Morphology progression: Lesions develop flaccid bullae and erosions within 24-48 hours of appearance; positive Nikolsky sign (epidermal sheet separation with light finger pressure) indicates extensive epidermal necrosis
• Distribution: Face, trunk, and extremities involved; palms and soles may be involved

Mucosal involvement (>90% of SJS cases):

• Oral mucosa: Oral erosions, severe stomatitis, difficulty eating/drinking; hemorrhagic crusts on lips (hallmark finding)
• Ocular: Conjunctival involvement (injection, conjunctivitis), eyelid involvement, severe cases develop symblepharon (eyelid adhesions) and conjunctival scarring
• Genital: Urethral or vaginal ulcerations, dysphagia, difficulty urinating
• Respiratory: Rare in SJS but may occur with airway involvement

Systemic manifestations: Fever (50-80% of cases), tachycardia, lymphadenopathy, and hepatomegaly. Multiorgan involvement including hepatitis, nephritis, and pulmonary involvement occurs in severe cases and predicts poor prognosis.

Diagnosis

Clinical diagnosis: Recognition of prodromal symptoms followed by rapid emergence of targetoid rash with mucous membrane involvement in the context of recent medication initiation is the key to diagnosis. Diagnostic criteria require: (1) widespread epidermal necrosis, (2) <10% BSA involvement, (3) mucous membrane involvement, and (4) recent medication use.

Histopathology: Punch biopsy from an early lesion shows: full-thickness epidermal necrosis with minimal dermal inflammation (distinguishes from severe erythema multiforme which shows preserved basal layer). Necrotic keratinocytes (apoptotic cells visible as round, dark-staining bodies) with sparse lymphocytic infiltrate. Late-stage lesions show subepidermal blistering and total epidermal necrosis. Immunohistochemistry may show CD8+ T cell infiltrate.

Laboratory findings: No specific lab test diagnoses SJS. CBC may show elevated WBC (>11,000/μL in 80% of cases), lymphopenia, or atypical lymphocytes. Electrolyte abnormalities reflect fluid losses from epidermal necrosis. Elevated transaminases, bilirubin, and creatinine indicate multiorgan involvement and poor prognosis.

Differential Diagnosis

Erythema multiforme (EM): EM has true target lesions (three zones: erythematous center, pale middle ring, red outer ring), involvement limited to distal extremities and face, minimal mucous membrane involvement (<25%), and preservation of basal keratinocytes on histology. EM is often viral-associated (herpes simplex), not drug-related.

Severe maculopapular exanthem: Drug rash may resemble SJS but lacks mucosal involvement and Nikolsky sign.

Toxic epidermal necrolysis (TEN): >30% BSA involvement defines TEN; treatment and prognosis differ from SJS.

Treatment

Immediate management:

• Drug discontinuation: IMMEDIATE discontinuation of all suspected medications is first-line therapy. Continuing the causative drug worsens outcomes and increases mortality 10-fold.
• Hospitalization: Admission to ICU or burn unit for continuous monitoring and supportive care
• Fluid resuscitation: Calculate fluid requirements using Parkland formula (2-4 mL × weight in kg × %BSA burned) or monitor urine output (goal 0.5 mL/kg/hour). Large-bore IV access required.
• Temperature management: Continuous monitoring; fever may indicate infection requiring antibiotics
• Nutritional support: Enteral feeding preferred; NG tube if mucositis prevents oral intake
• Pain management: Opioid analgesia (morphine 0.1-0.2 mg/kg/hour IV) essential for extensive erosions

Specific therapies:

• Systemic corticosteroids: Controversial; retrospective data suggests early high-dose corticosteroids (prednisone 1-2 mg/kg daily or methylprednisolone 1 g daily IV) started within first 24-48 hours may reduce mortality and progression. Should be tapered rapidly over 6-8 weeks. Limited by infection risk and other complications.
• Intravenous immunoglobulin (IVIG): 2 g/kg administered over 3-5 days; mechanism unclear but may block FasL-mediated apoptosis. Case series show potential benefit in early administration. Prospective data limited; expensive.
• Topical care: Sterile technique, frequent cleansing, occlusive dressings (like burn care), avoid adhesive dressings
• Antibiotic therapy: Reserve for documented bacterial infection; avoid prophylactic antibiotics (may select resistant organisms)
• Ocular care: Ophthalmology consultation essential; frequent eye cleansing, topical antibiotics, lubricants; avoid adhesive contact lenses; recognize symblepharon formation early to prevent permanent vision loss

Prognosis and Long-term Complications

Mortality: 1-5% in SJS, 25-35% in TEN. Mortality correlates with: percent BSA involved, age >40 years, cardiac involvement, elevated creatinine, elevated bilirubin, and female sex. Prognostic tools like SCORTEN (System for Organ failure assessment in Severe Cutaneous reactions) predict mortality based on: age >40, heart rate, temperature, serum glucose, urea, creatinine, and bicarbonate. Each point = 10-30% mortality increase.

Acute complications: Sepsis (20-30% of cases, major cause of death), multiorgan failure, fluid/electrolyte derangements, and disseminated intravascular coagulation (DIC).

Long-term complications: Ocular (symblepharon, conjunctival scarring, dry eyes, vision loss in 10-30%), esophageal strictures (post-re-epithelialization scarring), anal strictures, genital scarring causing urinary symptoms, and hypertrophic scars or pigmentation changes.

Prevention

Genetic testing: HLA testing (HLA-B*5701, HLA-A*31:01) before initiating high-risk drugs (abacavir, carbamazepine) in susceptible populations. Positive genotype is a relative contraindication unless no alternatives exist.

Risk mitigation: Educate patients about SJS warning signs (fever, painful rash, oral ulcers); advise immediate medical evaluation if these symptoms develop. Maintain medication allergy list documenting SJS/TEN reactions to inform future healthcare providers (significant cross-reactivity risk with structurally similar drugs, particularly among anticonvulsants).

Frequently Asked Questions

If I develop SJS to one antibiotic, can I take a different antibiotic?

Cross-reactivity varies by drug class. Beta-lactam cross-reactivity (penicillin to cephalosporin) is <2%, so alternative beta-lactams may be safe. However, anticonvulsant cross-reactivity is high (e.g., 20-80% cross-reactivity between carbamazepine and phenytoin). Any new drug in the same class carries increased risk (5-10% vs. baseline 1-2 per million). Desensitization to alternative drugs is occasionally performed under strict medical supervision, but most patients require complete avoidance of the entire drug class.

Will I always get SJS if I take the same drug again?

Re-exposure to the causative drug causes SJS recurrence in 25-100% of cases (highest with drugs like allopurinol and carbamazepine). Even small doses cause rapid, often more severe reactions. Permanent avoidance is recommended. Some individuals have documented tolerance induction with extremely slow escalation (desensitization under ICU conditions), but this is experimental and carries significant risk.

Can I get SJS from herbal or over-the-counter medications?

Yes, though rare. NSAIDs available OTC are well-established SJS causes. Herbal products are less commonly reported, but acetaminophen (available OTC) is documented as an SJS cause. The risk is lowest with most OTC drugs but exists. Report all medications, supplements, and herbal products to your dermatologist if you develop suspicious symptoms during drug use.

What does a positive Nikolsky sign mean?

A positive Nikolsky sign (gentle sliding finger pressure on apparently normal skin causes epidermis to separate and slough off) indicates extensive epidermal necrosis and apoptosis. This finding strongly suggests SJS/TEN but can occur with other conditions causing severe epidermal necrosis. In the context of recent drug use and rash, a positive Nikolsky sign is highly suggestive of SJS/TEN and warrants immediate hospital admission and drug discontinuation.

References