Hematochezia as the Initial Symptom in a Newborn With Factor XI Deficiency

Background The symptoms of factor XI (FXI) deficiency are generally mild. Cases of early diagnosis during the neonatal period are uncommon, particularly with hematochezia as an initial symptom. Case Presentation A male infant was born with a birth weight of 2368 g via an elective cesarean section at 38 weeks of gestation, without any family history of a bleeding disorder. On the fifth day after birth, he presented with bloody vomiting, and shortly thereafter, he passed dark red stools. He had a normal prothrombin time‐international normalized ratio, prolonged activated partial thromboplastin time (APTT) of 95.4 s, and FXI activity measuring < 3%. An APTT mixing test indicated a coagulation factor deficiency. Following the administration of fresh frozen plasma, the APTT of the patient improved, and his bloody stool disappeared. During hospitalization of the patient, prolonged APTT was observed again, but the bloody stool did not recur. His anemia progressed further, eventually necessitating blood transfusion. A small amount of hematochezia was evident after discharge; however, no transfusion was required to treat it. Genetic analysis revealed double heterozygous variants of the F11 gene (NM_000128.4; c.716T > C, p.Phe239Ser, and NM_000128.4; c.961_962del, p.Cys321HisfsTer37) on chromosome 4, confirming the diagnosis of FXI deficiency. Conclusions FXI deficiency presenting with hematochezia as the initial symptom in neonates is rare. Although FXI deficiency is commonly perceived as mild, the possibility of neonatal hematochezia in severe cases requires careful assessment and treatment.