Ribociclib-induced drug reaction with eosinophilia and systemic symptoms syndrome: report of two cases - 05/08/26

Doi : 10.1016/j.jahd.2026.100072

Aline Garcia ^a,^b,⁎ , Benoît Ben-Said ^a,^b,^c

^a Dermatology Department, hôpital Édouard-Herriot, Hospices civils de Lyon, Lyon, France

^b Université Claude-Bernard Lyon 1, Lyon, France

^c Dermatology and Clinical Immunology Department, Centre de référence des dermatoses bulleuses toxiques et toxidermies graves, hôpital Édouard-Herriot, Lyon, France

^⁎ Corresponding author.

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Highlights

•	Ribociclib-induced DRESS is rare but likely underreported.
•	DRESS should be considered when delayed rash and eosinophilia occur on ribociclib.
•	Within-class switch to palbociclib showed variable cross-reactivity outcomes.
•	Pharmacovigilance is needed for CDK4/6 inhibitor-induced severe drug reactions.

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Abstract

Background

Ribociclib, a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor, is widely used for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer. Drug reaction with eosinophilia and systemic symptoms is a rare but serious drug hypersensitivity reaction that has been only exceptionally reported with CDK4/6 inhibitors.

Cases

We describe two cases of ribociclib-induced drug reaction with eosinophilia and systemic symptoms syndrome, with onset 3 to 6 months after ribociclib initiation, presenting with cutaneous eruption, eosinophilia, and systemic involvement. Both patients improved after ribociclib discontinuation and corticosteroid therapy. One patient was successfully switched to palbociclib, whereas the other developed hepatotoxicity following the within-class switch to palbociclib.

Conclusions

These cases highlight the importance of recognizing drug reaction with eosinophilia and systemic symptoms syndrome as a potential complication of ribociclib therapy and support pharmacovigilance efforts regarding CDK4/6 inhibitor–associated severe cutaneous adverse reactions.

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Keywords : Breast cancer, CDK4/6 inhibitor, DRESS syndrome, Palbociclib, RegiSCAR, Ribociclib

Abbreviations : ALT, AST, CDK4/6, CMV, DRESS, EBV, HER2, HHV-6, PCR, RegiSCAR