Congenital protein C deficiency is a hereditary coagulation disease characterized by venous/arterial thrombosis secondary to the reduction of protein synthesis and/or activity. It is well known that severe congenital protein C deficiency can occur with thrombosis severe, systemic symptoms, sometimes immediately after birth, with poor prognosis.1 We present a case in which the finding of thrombosis of the renal vein and renal infarction in two newborns (2015 and 2017), has subsequently allowed to diagnose an unknown deficiency of functional protein C in the mother with a history of obstetric complications.