F5 and hyperinsulinemic hypoglycemia, familial, 4: In FMCFDs arising from a single-gene defect, such as combined FV and FVIII deficiency and combined deficiency of the vitamin K–dependent factors, genetic variants in the genes encoding proteins responsible for the intracellular trafficking of FV and FVIII, (multiple coagulation factor deficiency 2 (MCFD2) and lectin mannose-binding 1 (LMAN1)) and genetic variants in genes encoding enzymes involved in post-translational modification and vitamin K metabolism (γ-glutamylcarboxylase (GGCX) and vitamin K epoxide reductase complex subunit 1 (VKORC1)) are reported [7,20,21,22].