Abstract
BACKGROUND: Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a rare life-threatening thrombotic reaction to COVID-19 vaccines. CASE DESCRIPTION: Two young male first cousins, with a family history of idiopathic thrombocytopenic purpura, developed VITT after the Ad26.COV2.S vaccine. Both had a favourable clinical and analytical outcome. We investigated the genetic factors that could be associated with a genetic predisposition to VITT. CONCLUSIONS: There are no published cases where the VITT patients were relatives. The genetic study did not reveal any likely pathogenic variants, although the prevalent polymorphism c.497A>G (p.(His166Arg)) in the FCGR2A gene was found in a homozygous state. More studies are required to better understand VITT's pathophysiology and any underlying genetic predispositions. LEARNING POINTS: Vaccine-induced immune thrombotic thrombocytopenia (VITT), a rare but life-threatening disease, emerged with COVID-19 vaccines.The genetic analyses revealed the FCGR2A gene in a homozygous state.These cases may raise new questions about a family predisposition to VITT.