Hematological studies indicated the cause of the venous sinus thrombosis was a primary thrombophilia caused by a heterozygous MTHFR mutation variant p.Ala222Val and a 35% decrease in plasmatic protein S. Conclusions: This case highlights the possible relationship between psychiatric and thrombotic disorders, suggesting that both the MTHFR mutation and protein S deficiency could lead to psychotic disorders. The gene discussed is PROS1; the disease is hyperinsulinemic hypoglycemia, familial, 4.