Evidence of the molecular epidemiology of thrombophilia is growing, and the clinical management of adult thromboembolism patients has recently made significant progress. On the other hand, there is little or no evidence concerning the genetic variation, treatment, and prophylaxis of thromboembolism development in the early life stage. The clinical presentation of early-onset thrombosis/thrombophilia, which mostly occurs in newborns and adolescents, differs from that in cases of adult-onset. Recurrent purpura fulminans and/or intracranial hemorrhage/infarction leads to dangerous lifelong complications. As in the setting of cancer genomic medicine, germline variants require determination for the individualized control of early-onset thrombophilia. The genetic predisposition to thrombosis varies among ethnicities. In the Japanese population, the protein S variant (PS-Tokushima, K196E) has attracted attention as the cause of a common and low-risk prothrombotic predisposition in adults, while protein C deficiency greatly impacts the onset of pediatric thrombosis. In 2020, 3 years after the registration of idiopathic thrombosis as a designated intractable disease, genetic tests have been promulgated for health insurance portability. Disease-specific therapy for early-onset thrombophilia is crucial. Here, we review the genetic heterogeneity, prophylaxis, and treatment strategy of the rare subgroups of severe heritable thrombosis conditions in Japan.
Keywords: Protein C; Protein S; Purpura fulminans; Thrombophilia.