SERPINE1 and Venous thrombosis: This study in pediatric patients was designed under the guiding hypothesis of a possible regulatory interplay between miR-145 and miR-34a expression and PAI-1 fluctuations, which are documented in the literature for hypofibrinolysis in adult thrombosis [5,15,22,23], across different stages of post-thrombotic course and treatment, as well as the different genotypes of the 4G/5G and I/D functional variants.