This is a literature report for the following literature source(s): "TOXIC EPIDERMAL NECROLYSIS FOLLOWING MACROPHAGE ACTIVATION SYNDROME", Annals of Allergy, Asthma and Immunology., 2021; Vol:127(5 Suppl.), pgs:S66, DOI:10.1016/j.anai.2021.08.203. A 23 year-old female patient received COVID-19 Vaccine - Manufacturer Unknown, (Batch/Lot number: unknown) as dose 2, single for Covid-19 immunisation. The patient's relevant medical history and concomitant medications were not reported. Vaccination history included: Covid-19 vaccine (Dose 1, Manufacturer unknown), for COVID-19 immunisation. The following information was reported: HAEMOPHAGOCYTIC LYMPHOHISTIOCYTOSIS (hospitalization, medically significant), outcome "recovered", described as "The widespread innate immune activation from MAS, possibly triggered by preceding vaccination"; TOXIC EPIDERMAL NECROLYSIS (prolonged hospitalization, medically significant), outcome "recovered", described as "augmented her risk of developing TEN". Therapeutic measures were taken as a result of haemophagocytic lymphohistiocytosis, toxic epidermal necrolysis. Clinical course: Introduction: The risk of toxic epidermal necrosis (TEN) depends on both drug and host factors, such as autoimmune disease. The authors present a case of TEN in a patient with recently diagnosed macrophage activation syndrome (MAS). Case Description: A 23-year-old previously healthy woman was admitted multiple times over 4 weeks for spiking fevers, cervical lymphadenopathy, and macular rash. Her symptoms began one week after her second SARS-CoV-2 mRNA vaccine and did not respond to outpatient treatment with azithromycin and steroids for presumed upper respiratory infection. Extensive infectious evaluation was unrevealing. She had elevated liver enzymes, cytopenias, lymphadenopathy, and splenomegaly. Lymph node and bone marrow biopsies were unrevealing. Further evaluation demonstrated elevated triglycerides, ferritin, and soluble IL-2 receptor. Natural killer cell function was normal. IL-18 was markedly elevated (181,803 pg/mL) supporting the diagnosis of adult-onset Still's disease with MAS. Dexamethasone and anakinra were initiated on day 29 of illness with prophylactic atovaquone and pantoprazole. Her symptoms and labs improved until day 57 of illness when she developed a diffuse, painful, blistering maculopapular rash consistent with TEN. Potential culprit drugs were held (pantoprazole, atovaquone, and cephalosporins) and she received a short course of MG and cyclosporine in addition to anakinra and steroids. She required prolonged hospitalization for wound care and rehabilitation. She has recovered well and remains on prednisone and canakinumab. Discussion: The widespread innate immune activation from MAS, possibly triggered by preceding vaccination, may have augmented her risk of developing TEN. Treatment was therefore directed towards ongoing MAS in addition to TEN. Inflammatory markers, illness events, and treatments are displayed chronologically according to days from initial onset of macrophage activation syndrome. Lab values are normalized for comparison. Sender's Comments: Based on the current available limited information in the case provided, the causal association between the event and the use of suspect product BNT162B2 cannot be fully excluded. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to RAs, Ethics Committees, and Investigators, as appropriate.