MTHFR and hyperhomocysteinemia: The pathophysiology of the thromboembolic phenomena associated with CD [10-26] represents a puzzle with multiple constituents: hyperhomocysteinemia; B12 and\or folate deficiency; methylenetetrahydrofolate reductase mutations; the high homology between blood coagulation factor XIII and tTG; and protein C and S deficiency due to vitamin K deficiency [21-26,54].