• April 2025: Non–small cell lung cancer (NSCLC)
  • June 2025: Five cycles of platinum-based chemotherapy; discontinued due to toxicity
• May 2025: Metastatic cancer of unknown primary (CUP), nodal manifestation
  • Histology: moderately differentiated, p16-positive squamous cell carcinoma (DD anal carcinoma; DD cervical carcinoma)

• September 2025: First administration of atezolizumab monotherapy

Three weeks after the first atezolizumab infusion, the patient presented with high fever, severe mucositis, conjunctivitis, and intense ocular pain preventing eye opening. A skin biopsy confirmed Stevens–Johnson syndrome / toxic epidermal necrolysis (SJS/TEN) overlap.

The patient received high-dose methylprednisolone, broad-spectrum antibiotics, IV acyclovir, intensive topical dermatologic and ophthalmologic treatment, strong opioid-based analgesia, and parenteral nutrition. Due to ongoing symptoms, a therapy escalation using IVIG and mycophenolate mofetil was performed and the case was discussed in our interdisciplinary Toxboard. Afterwards, oral erosions, cutaneous and ocular findings improved significantly.

Immune checkpoint inhibitor (ICI)–associated SJS/TEN overlap is a very rare but life-threatening immune-related adverse event with an estimated incidence below 0.01%. Clinically, patients show rapidly progressive erythema and atypical target lesions, with epidermal detachment ranging from <10% in SJS, 10–30% in SJS/TEN overlap, to >30% in TEN. Mucosal involvement—ocular, oral, or genital—is frequent. Prognosis is commonly estimated using SCORTEN. It is thought to result from ICI-induced hyperactivation of cytotoxic CD8⁺ T cells and overexpression of effector molecules such as perforin, granzyme B, FasL, and granulysin, leading to widespread keratinocyte apoptosis. Compared with classical drug-induced SJS/TEN overlap, latency may be longer and onset can occur up to 8 weeks after treatment initiation. Early recognition, immediate discontinuation of the ICI, systemic corticosteroids, escalation to IVIG or other immunomodulators, and optimal supportive care are crucial for outcome.

1. Chirasuthat P, Chayavichitsilp P. Atezolizumab-induced Stevens-Johnson syndrome in a patient with non-small cell lung carcinoma. Case Rep Dermatol. 2018;10(2):198–202. doi:10.1159/000492172. 
2. Nordmann TM, Anderton H, Hasegawa A, et al. Spatial proteomics identifies JAKi as treatment for a lethal skin disease. Nature. 2024;635(8040):1001-1009. doi:10.1038/s41586-024-08061-0
3. Satoh TK, Neulinger MM, Stadler PC, Aoki R, French LE. Immune checkpoint inhibitor-induced epidermal necrolysis: a narrative review evaluating demographics, clinical features, and culprit medications. J Dermatol. 2024;51(1):3–11. doi:10.1111/1346-8138.17039.