An Uncommon Case of Siblings With Homozygous Prothrombin G20210A Pathological Variant Expressing as Unique Manifestations

Heterozygous carriers of the prothrombin gene G20210A pathogenic variant (PV), with a 1.7% to 3% prevalence, experience a 3-fold increase in risk for thrombosis. Homozygosity for the prothrombin G20210A PV is much less common, with a prevalence of 0.014%, and further increases the risk for thrombosis, although data is insufficient to predict the increased likelihood. While venous thrombi and pulmonary emboli (PE) are common manifestations of this PV, portal vein thrombosis (PVT) and neuropsychiatric disorders are uncommon manifestations. We present a pair of siblings who are homozygous for this prothrombin G20210A PV.