Stevens-Johnson Syndrome: Severe Drug Reaction

Clinical Overview

Stevens-Johnson Syndrome (SJS) is a rare but severe mucocutaneous reaction characterized by widespread epidermal necrosis and detachment affecting less than 10% of body surface area (BSA). The condition lies on a spectrum of severe cutaneous adverse reactions (SCAR) that includes Toxic Epidermal Necrolysis (TEN, affecting >30% BSA) and overlap SJS/TEN (10-30% BSA). SJS carries a mortality rate of 1-5%, with higher rates in elderly patients and those with delayed recognition. Early identification and causative drug discontinuation are critical for improving outcomes.

Epidemiology & Risk Factors

SJS affects approximately 1-6 cases per million person-years, making it rare but not exceptionally so in dermatologic practice. Incidence increases with age, with median onset around 40 years. Medications account for 80-90% of cases, with NSAIDs, antibiotics (particularly sulfonamides), anticonvulsants (phenytoin, carbamazepine, lamotrigine), and allopurinol as the most common culprits. Allopurinol carries a 25-50 fold increased risk. Genetic factors, particularly HLA-B*5801 in Asian populations and HLA-A*3101 with carbamazepine, significantly influence susceptibility. HIV/AIDS patients have 100-1000 times higher risk than the general population. Prior episodes of SJS substantially increase recurrence risk with the same or structurally similar drugs.

Pathophysiology

SJS results from a CD8+ T cell-mediated toxic reaction to drug metabolites presented on keratinocyte surfaces via MHC Class I molecules. The drugs undergo hepatic metabolism to reactive intermediates that act as haptens, binding to proteins and creating foreign antigens. Key cytotoxic mediators include perforin and granzyme B, which create apoptotic pathways in keratinocytes. FasL-Fas interactions and TNF-alpha signaling further amplify keratinocyte death. The resulting massive epidermal-dermal separation leads to fluid loss, infection risk, and multi-organ involvement through systemic cytokine release.

Clinical Presentation & Classification

SJS typically begins 1-8 weeks after drug initiation with prodromal symptoms: fever (often >39°C), malaise, arthralgia, and respiratory symptoms lasting 1-3 days. Mucosal involvement (oral, ocular, genital, respiratory) precedes skin manifestations in 90% of cases. Patients develop painful erosions on lips, buccal mucosa, and pharynx. Characteristic skin lesions are targetoid macules (true targets with three zones: dusky center, pale middle ring, red outer halo) or atypical targets, typically on face, trunk, and proximal extremities with acral predominance. Widespread lesions progress to large confluent areas of epidermal detachment. Systemic features include hepatitis, nephritis, pneumonitis, myocarditis, and hematologic abnormalities.

SJS is classified by extent of BSA involved:

• SJS: <10% BSA detachment
• SJS/TEN overlap: 10-30% BSA detachment
• TEN: >30% BSA detachment

Diagnosis & Workup

Clinical diagnosis is based on characteristic morphology and mucosal involvement, but skin biopsy provides confirmation. Histopathology shows full-thickness epidermal necrosis with minimal inflammation (distinguishing from TEN variants and other conditions). Suprabasal acantholysis and basal layer vacuolization are typical findings. Direct immunofluorescence is negative, ruling out immune blistering diseases.

Diagnostic workup includes:

• Complete metabolic panel, liver function tests, and CBC
• Blood cultures if febrile (assess for superinfection)
• Ophthalmologic evaluation for conjunctival involvement
• Chest imaging if respiratory symptoms present
• ECG if cardiac involvement suspected
• Careful documentation of mucosal involvement (SJS requires oral or genital mucosa involvement plus skin lesions)

Scoring systems like the RegiSCAR scoring system (validated for SJS/TEN) help confirm diagnosis: scores >2 suggest probable case, >4 indicate definite case.

Treatment Algorithm

Immediate management: Upon clinical suspicion, discontinue the causative drug immediately. There is no safe re-challenge. Refer to burn center or ICU-level care. Avoid antibiotics unless proven infection (colonization is common but doesn't require treatment). NSAIDs and acetaminophen should be discontinued due to potential cross-reactivity.

Supportive care (cornerstone of treatment): This includes nursing care comparable to burn units, fluid and electrolyte management to prevent hypovolemic shock, nutritional support via tube feeding when oral intake is compromised, infection prevention with sterile dressings, and pain management with opioids. Avoid adhesive dressings; use non-adherent materials.

Systemic corticosteroids: Evidence is mixed but current practice favors early, high-dose corticosteroids. Typical regimen: methylprednisolone 1-2 g IV daily or prednisone 1-2 mg/kg/day oral, tapered over 6-12 weeks. The ALDEN study (2016) suggests steroids reduce mortality and hospital stay. However, late initiation (>3-5 days) is less effective.

Intravenous immunoglobulin (IVIG): Retrospective data suggest IVIG 2 g/kg over 3-5 days may improve mortality, particularly when started early. Some guidelines recommend IVIG as alternative to or in addition to steroids, though robust RCT evidence is lacking. The TEN-EASED prospective study is ongoing.

Other agents under investigation: TNF-alpha inhibitors, cyclosporine, plasmapheresis, and other immunosuppressants have anecdotal support but lack strong evidence. Tacrolimus applied topically to mucosal erosions may provide symptom relief.

Prognosis & Complications

Mortality in SJS ranges from 1-5%, compared to 20-40% in TEN. Key prognostic factors include age >40 years, malignancy, renal dysfunction, and >50% BSA involvement. Long-term sequelae are common: ocular scarring (50-75% of patients), leading to dry eye, trichiasis, symblepharon, and vision loss; esophageal strictures (40% of survivors); and psychological effects including PTSD and depression. Fertility may be affected by genital scarring.

When to See a Dermatologist

Seek emergency dermatology evaluation immediately if you develop widespread targets or atypical targets, fever, and oral erosions, particularly within 1-8 weeks of starting a new medication. Do not delay—early recognition dramatically improves survival. Patients with SJS require hospitalization in burn centers or ICUs. After acute resolution, long-term follow-up with dermatology is essential for surveillance of cutaneous sequelae and confirmation that causative drugs are avoided forever.

Frequently Asked Questions

Can SJS recur if I avoid the causative drug?

Recurrence is extremely rare if the causative drug is completely avoided. However, cross-reactivity with structurally similar drugs (e.g., other anticonvulsants in the same class) occurs in 25-30% of cases. Maintain an updated drug allergy list and always inform healthcare providers of your SJS history. Genetic testing (HLA-B*5801 for allopurinol, HLA-A*3101 for carbamazepine) may help guide future medication choices.

What is the difference between SJS and TEN?

The distinction is based on percentage of BSA with full-thickness epidermal detachment: SJS involves <10% BSA, SJS/TEN overlap involves 10-30% BSA, and TEN involves >30% BSA. TEN has a mortality rate of 20-40% compared to 1-5% for SJS, but both are medical emergencies requiring immediate hospitalization.

How long does recovery take?

Acute phase typically lasts 2-4 weeks with appropriate care. Epithelialization usually completes within 3-6 weeks. However, psychological recovery and management of long-term complications may take months to years. Post-inflammatory hyperpigmentation can persist for 6-12 months.

Are topical steroids safe for healing skin?

Topical corticosteroids are generally avoided during acute phase to prevent masking early signs of superinfection. However, after acute phase resolution, topical corticosteroids (Class III-IV) may help manage post-inflammatory erythema and support faster re-epithelialization. Tacrolimus ointment is safe for mucosal areas and may reduce pain.

References