The aim of this study was to investigate the possible role of FXIII activity and three genetic variants of the THBS4 gene, namely, Val34Leu (rs5985: C > A) of F13A1, T/G 3′UTR (rs8089: T > G) of THBS2 and Ala387Pro (rs1866389: G > C), in the development of MI in young patients. The gene discussed is THBS2; the disease is myocardial infarction.