SJS/TEN Triggers: Medications, Infections, and Genetic Risks Explained
Exploring the diverse triggers and risk factors that precipitate Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis.
Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) are severe, life-threatening mucocutaneous adverse reactions characterized by widespread epidermal necrosis and detachment, primarily triggered by medications, infections, or genetic susceptibilities. These conditions exist on a spectrum, with SJS involving less than 10% body surface area detachment, overlap 10-30%, and TEN over 30%, often sharing identical triggers but differing in severity.
What are the triggers of SJS/TEN?
The most common triggers for SJS/TEN are medications, accounting for over 80% of cases, particularly in adults, while infections predominate in children. High-risk drugs include allopurinol, carbamazepine, sulfonamides, and lamotrigine, with onset typically 1-4 weeks after initiation. Genetic factors, such as HLA-B*15:02 allele, strongly predispose certain populations to carbamazepine-induced SJS/TEN. Other triggers encompass vaccinations, autoimmune conditions, and rarely, physical agents like radiation.
High-risk medications
Certain medications pose the highest risk for inducing SJS/TEN due to their reactive metabolites or immune-mediated mechanisms. Allopurinol, used for gout and hyperuricemia, has the highest reported odds ratio (OR 108.4), especially in patients with renal impairment or concomitant diuretics. Anticonvulsants like carbamazepine (OR 52.0), phenytoin, and lamotrigine follow closely, with risks amplified in first-time exposures.
- Allopurinol: Highest risk; avoid in HLA-B*58:01 carriers (e.g., Han Chinese, Thai populations).
- Carbamazepine: Screen for HLA-B*15:02 in Asian ancestry before prescribing.
- Sulfonamide antibiotics (e.g., sulfamethoxazole): Common in HIV patients; OR 112 for trimethoprim-sulfamethoxazole.
- Lamotrigine: Risk increases with rapid titration; slow initiation reduces incidence.
- NSAIDs (e.g., oxicams like piroxicam): Phototoxicity enhances risk.
Less common but notable risks include beta-lactam antibiotics, nevirapine (in HIV therapy), and newer immunomodulators like PD-1 inhibitors. Cold medicines combining multiple drugs (e.g., antipyretics + cold remedies) elevate risk multiplicatively.
Medium-risk medications
Medications with moderate risk (OR 3-20) warrant caution, particularly in polypharmacy or high-risk patients. These include cephalosporins, quinolones (e.g., ciprofloxacin), tetracyclines, and proton pump inhibitors like esomeprazole. Antiretrovirals such as abacavir and nevirapine carry elevated risks in HIV populations, often linked to immune reconstitution.
| Drug Class | Examples | Reported OR |
|---|---|---|
| Antibiotics | Cephalexin, Ciprofloxacin | 5-15 |
| Antiretrovirals | Nevirapine, Abacavir | 10-50 |
| Proton Pump Inhibitors | Esomeprazole | ~5 |
| Others | Diltiazem, Terbinafine | 3-10 |
Risk is dose-dependent and higher with first prescriptions or re-exposures.
Low-risk medications
Drugs with low but documented risk (OR <3) include acetaminophen, ibuprofen (non-oxicam NSAIDs), and insulin. These are safer alternatives but vigilance is needed in patients with prior SJS/TEN history.
Immunologically-mediated drug mechanisms
SJS/TEN pathogenesis involves drug presentation by HLA molecules to cytotoxic T-cells, triggering Fas-FasL mediated keratinocyte apoptosis and granulysin release. High-risk HLA alleles (e.g., HLA-B*15:02 for carbamazepine) facilitate this ‘p-i concept’ (pharmacological interaction), bypassing typical immune processing. Cytotoxic proteins like granulysin dominate in TEN dissemination.
Genetic predisposition
Genome-wide studies identify HLA class I alleles as key predictors: HLA-B*15:02 (carbamazepine in Asians, OR 94), HLA-B*58:01 (allopurinol, OR 107 in Han Chinese), HLA-B*15:08 (carbamazepine in Europeans), and others like HLA-A*31:01. Pharmacogenetic screening is recommended by FDA/EMA for at-risk populations, reducing incidence by up to 80% in screened cohorts.
Infectious disease triggers
Infections trigger ~10% of SJS/TEN, mainly in children: Mycoplasma pneumoniae (30% of pediatric cases), cytomegalovirus (CMV), herpes simplex virus (HSV), and rarely COVID-19 or influenza. These mimic drug reactions but lack drug exposure history; biopsy shows similar necrolysis.
Infection-associated SJS/TEN in children
Mycoplasma pneumoniae accounts for 50-80% of infection-related pediatric SJS/TEN, often without mucosal involvement or severe detachment. Prolonged fever precedes rash; macrolides may paradoxically trigger. Other culprits: EBV, enteroviruses.
Other triggers
- Vaccinations: Rare post-vaccination cases (e.g., influenza, COVID-19 mRNA vaccines); temporal association <2 weeks.
- Autoimmune diseases: Linked to SLE, dermatomyositis; Sweet syndrome overlap reported.
- Radiotherapy/UV: Localised TEN in treated fields.
- Others: Contrast media, illegal street heroin.
SJS/TEN after mRNA COVID-19 vaccines
Extremely rare (<1/million doses); 20+ cases reported, median onset 6 days post-vaccination. Mostly SJS-like with recovery; no specific HLA link identified.
Management of drug triggers
Immediate drug cessation is paramount (reduces mortality 30-50%). Avoid re-exposure to culprit or related drugs. Supportive care in burn ICU: fluids, nutrition, wound care, infection prophylaxis. Immunomodulators (IVIG, cyclosporine) controversial but used early.
Prevention
Screen high-risk patients: HLA-B*15:02 before carbamazepine in Asians, HLA-B*58:01 before allopurinol in Koreans/Chinese. Use lowest effective doses, slow titrations. Educate on prodromal flu-like symptoms (fever, sore throat, rash) for early cessation. Registries like EuroSCAR inform risk stratification.
Frequently Asked Questions (FAQs)
Q: What is the most common trigger for SJS/TEN?
A: Medications, especially allopurinol, carbamazepine, and sulfonamides, trigger over 80% of cases.
Q: Should genetic testing be done before starting certain drugs?
A: Yes, HLA-B*15:02 screening before carbamazepine in Asian patients and HLA-B*58:01 before allopurinol in at-risk ethnicities.
Q: Can infections cause SJS/TEN?
A: Yes, particularly Mycoplasma pneumoniae in children; also CMV, HSV.
Q: What are early warning signs of SJS/TEN?
A: Prodrome of fever, malaise, sore throat, followed by targetoid rash and mucosal erosions.
Q: Is SJS/TEN contagious?
A: No, it is a hypersensitivity reaction, not infectious.
Clinical Images Description
Typical SJS/TEN features erythematous target-like lesions with central duskiness, epidermal detachment, and hemorrhagic mucosal crusting on lips, eyes, genitals. Full-thickness necrosis evident on biopsy.
References
- Dermatologic Manifestations in Sjögren’s Syndrome — Robert I. Fox, MD. 2000. https://robertfoxmd.com/SjogrensByFox/Dermatologic_Manifestations.pdf
- A bitter-Sweet syndrome with potential autoimmune connections — Medsafe New Zealand. 2020-12-01. https://www.medsafe.govt.nz/profs/PUArticles/December2020/bitter-Sweet-syndrome-potential-autoimmune-connections.html
- Sjogren syndrome: Symptoms, Causes, and Treatment — DermNet NZ. 2023. https://dermnetnz.org/topics/sjoegren-syndrome
- Skin signs of rheumatic disease — DermNet NZ. 2023. https://dermnetnz.org/topics/skin-signs-of-rheumatic-disease
- Ask the Expert: Skin Rashes and Sjögren’s — Sjögren’s Foundation. 2019-07-01. https://sjogrens.org/blog/2019/ask-the-expert-skin-rashes-and-sjogrens
- Sjögren syndrome image — DermNet NZ. 2023. https://dermnetnz.org/imagedetail/2550-sjoegren-syndrome
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