A 15-year-old female presented to the emergency depament with history of recurrent epistaxis, Hematuria and hematochezia. There was a history of profuse bleeding from the umbilicus stump at bih. Previous investigations revealed normal prothrombin time, activated paial thromboplastin time, thrombin time and fibrinogen levels. Her platelet counts as well as platelet function tests were normal but urea clot lysis test was positive. Which one of the following clotting factor is most likely to be deficient?

- History given in question suggests diagnosis of Factor XIII deficiency. Factor XIII deficiency (Fibrin stabilizing factor or transglutaminase deficiency): Clinical symptoms include history of bleeding from umbilical stump, recurrent episodes of epistaxis, Hematuria and hematochezia As factor XIII is responsible for the cross linkage of fibrin & stabilizing the fibrin clot, symptoms of delayed hemorrhage are secondary to the clot instability PT , aPTT , Thrombin time & fibrinogen levels are normal The normal clot remains insoluble in the presence of urea, whereas in a patient with factor XIII deficiency, the clot dissolves due to failure of cross linking.