Stevens-Johnson syndrome related with Comirnaty® coronavirus disease 2019 vaccine.

Stevens-Johnson syndrome is a rare severe delayed-type hypersensitivity reaction. Even though not initially described as a side-effect of the Comirnaty® coronavirus disease 2019 (COVID-19) Vaccine, the worldwide public COVID-19 vaccination programs are uncovering this serious adverse event. We present the case of a 44-year-old woman, vaccinated with the 1st dose in July 2021, and the 2nd dose 4 weeks later. Five days after the 2nd dose, a 10 cm, circular, painful, violet/red lesion appeared on the injection site. From then on, multiple, generalized purpuric painful lesions appeared, associated with ulcers on the lips, oral cavity, nasal cavity, vulva, and vagina, oedema of the hands and feet, conjunctival erythema, blurred vision, and malaise. The patient was being treated with lamotrigine and sodium valproate (for 2 years, without interruptions or dose change) which were stopped, and the patient started treatment with systemic corticosteroids. Lymphocyte transformation test were performed and were positive for PEG2000 1 µg/mL (stimulation index [SI], 30.9), and the undiluted Comirnaty® vaccine (SI, 32.2). These tests were negative on several vaccinated controls. We can definitively show that sensitization to the vaccine and PEG2000 can occur. A more extensive evaluation and reporting is needed to know the true incidence of this life-threatening condition and possible risk factors; as not only further booster shots of this vaccine will be administered, but also new vaccines with the mRNA technology are likely to be more prevalent in the future.