SJS vs. TEN: What’s the Difference and Why It Matters

Stevens–Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) are two names you may have seen used together, and for good reason. These conditions are rare, severe skin reactions often triggered by medications or infections. They share many symptoms and treatments, which is why they’re often grouped as “SJS/TEN.” The main difference lies in the extent of skin detachment, which reflects the severity of the condition at the time of diagnosis.

Let’s break it down.

It All Comes Down to Skin Involvement

The difference between SJS and TEN is how much of the body’s skin surface is affected:

●      SJS is diagnosed when less than 10% of the body’s surface area has skin detachment (like blisters or peeling).

●      TEN is diagnosed when more than 30% of the skin is involved.

●      Cases that fall between 10–30% are called SJS/TEN overlap.

This matters because the more skin that’s affected, the higher the risk of serious complications like infections, dehydration, and organ damage. TEN has a much higher mortality rate than SJS because of how widespread the damage can be.

Similar Causes, Similar Symptoms

Both SJS and TEN are considered severe drug reactions in most cases. Common culprits include antibiotics (like sulfa drugs) and seizure medications. Symptoms often start with flu-like feelings (fever, sore throat, body aches) followed by painful rashes, blistering, and sloughing of the skin and mucous membranes (such as the mouth, eyes, or genitals).

Patients may be treated in burn units because the damage resembles severe burns. Treatment focuses on stopping the medication that triggered the reaction, controlling symptoms, and preventing infection. Supportive care is crucial, and for TEN in particular, the need for intensive care is often urgent.

What Makes TEN So Dangerous?

While SJS and TEN are different points on the same spectrum, the degree of skin detachment has important clinical implications. When over 30% of the skin barrier is compromised, the body becomes vulnerable to life-threatening infections, severe fluid loss, and temperature regulation problems. In fact, some studies report mortality rates for TEN as high as 30–50%, compared to 5–10% for SJS.

There’s also a higher likelihood of systemic involvement, such as lung, kidney, and liver damage, in TEN patients. That’s why early diagnosis and transfer to a specialized care unit is critical.

How Do Doctors Tell Them Apart?

Doctors use something called the body surface area (BSA) rule, which is borrowed from burn medicine, to classify the condition. They also pay attention to the speed of progression, the presence of mucosal involvement (which is nearly always affected), and lab markers that can predict severity.

One widely used tool is the SCORTEN score, which helps estimate the severity of illness based on several factors including age, heart rate, and the extent of skin detachment. The higher the score, the higher the risk, especially in TEN.

Why This Distinction Matters

Knowing whether someone has SJS or TEN, affects the care people receive from hospital triage to follow-up treatment. It can influence:

●      What kind of unit the patient is transferred to (burn unit, ICU, etc.)

●      What specialists are involved (dermatologists, ophthalmologists, infectious disease experts)

●      What kinds of long-term issues to monitor for (like vision problems or psychological trauma)

It also helps researchers better understand how to improve treatments and outcomes. Most importantly, it allows survivors and their families to find resources and support tailored to their experience.

The Takeaway

SJS and TEN are part of the same spectrum, but they aren’t identical. The key difference surrounds how much skin is affected, and shapes the risk, the treatment, and the recovery. Knowing the distinction helps patients get the care they need, faster.

And whether it’s 10% or 90% of the skin, both SJS and TEN are serious conditions that deserve compassion, awareness, and support far beyond the hospital walls.

References

1. Frantz R, Huang S, Are A, Motaparthi K. Stevens–Johnson syndrome and toxic epidermal necrolysis: a review of diagnosis and management. Medicina. 2021 Aug 28;57(9):895.

   
   

2. Zimmerman D, Dang NH. Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) immunologic reactions. Oncologic Critical Care. 2020:267-80.

   
   

3. Hama N, Aoki S, Chen CB, Hasegawa A, Ogawa Y, Vocanson M, Asada H, Chu CY, Lan CC, Dodiuk-Gad RP, Fujiyama T. Recent progress in Stevens–Johnson syndrome/toxic epidermal necrolysis: diagnostic criteria, pathogenesis and treatment. British Journal of Dermatology. 2025 Jan;192(1):9-18.

   
   

4. Shah H, Parisi R, Mukherjee E, Phillips EJ, Dodiuk-Gad RP. Update on Stevens–Johnson syndrome and toxic epidermal necrolysis: diagnosis and management. American Journal of Clinical Dermatology. 2024 Nov;25(6):891-908.

   
   

5. Wasuwanich P, So JM, Chakrala TS, Chen J, Motaparthi K. Epidemiology of Stevens-Johnson syndrome and toxic epidermal necrolysis in the United States and factors predictive of outcome. JAAD international. 2023 Dec 1;13:17-25.