Catastrophic antiphospholipid syndrome after COVID-19 mRNA vaccination: A case report

Objective Antiphospholipid syndrome (APS) is a common acquired thromboinflammatory disease and catastrophic APS (CAPS) its most rare and lethal variant. The objective of this report is to describe a case of probable CAPS triggered after vaccination with an mRNA vaccine in the context of the COVID-19 pandemic. Methods This is a descriptive case report conducted at a Brazilian university hospital, involving a single 40-year-old patient admitted with dysarthria, gross hematuria, signs of pulmonary embolism, and a large intracavitary cardiac thrombus. He had a history of multiple past venous thrombotic events, but investigations for malignancy had consistently yielded negative results. Approximately 48 hours earlier, he had received the second dose of the Pfizer® mRNA vaccine (Pfizer-BioNTech BNT162b2). After infections and concomitant autoimmune diseases were ruled out, thrombocytopenia and positive serologic testing for APS raised the possibility of CAPS, and treatment was promptly initiated with anticoagulation, corticosteroids, low-dose aspirin, and hydroxychloroquine. Main outcome measures were organ involvement, laboratory abnormalities, imaging findings, and clinical response to treatment. Results After therapeutic measures were instituted, the patient showed laboratory improvement — restoration of renal function and increased platelet count — as well as clinical improvement, with resolution of neurological deficits. Follow-up testing revealed persistent triple positivity for APS-related serologies. Conclusions This emblematic report brings a rare complication of APS in association with immunization using an mRNA COVID-19 vaccine, presenting clinical features that resemble those described in other CAPS cases documented in the CAPS Registry. Additional reports of immune-mediated diseases induced by vaccine platforms have also been described, suggesting pathophysiological mechanisms that remain incompletely understood, particularly molecular mimicry. Immunization against COVID-19 and other pathogens should not, however, be discouraged, as vaccines continue to play a fundamental role in preventing potentially severe infectious diseases. Instead, scientific research should be encouraged in order to better understand which individuals are more predisposed to such a severe complication.