As for types of HT: 25 (45.5%), alteration of the methylenetetrahydrofolate reductase (MTHFR) gene; 20 (36.4%), factor XII gen alteration; 5 (9.1%), alteration in prothrombin; 4 (7.3%), protein S deficiency; and 1 (1.7%), factor V Leiden alteration. The gene discussed is F2; the disease is hematocrit.