Recurrent Subdural Hematoma Revealing Undiagnosed Mild Hemophilia A and Factor XIII Deficiency in an Elderly Patient.

Recurrent acute subdural hematoma (ASDH) is uncommon and typically associated with trauma, vascular malformations, or coagulopathies. While hemophilia is usually diagnosed in childhood, mild forms may remain undetected until adulthood, potentially presenting with unexpected perioperative bleeding. We report the case of a 75-year-old male who sustained a traumatic head injury resulting in ASDH along the falx cerebri and left frontotemporal region. Initial conservative management was followed by neurological deterioration associated with worsening cerebral edema, requiring emergent craniotomy. Postoperative rebleeding occurred twice, necessitating a total of three craniotomies. A coagulation workup after the second reoperation revealed decreased factor VIII ([FVIII] 22%) and factor XIII ([FXIII] 53%) activity. Although FVIII activity had not been checked initially, it remained consistently low during follow-up. The FVIII inhibitor test was negative, and a cross-mixing test supported the diagnosis of congenital hemophilia A. Genetic testing was not performed due to cost and patient preference. After initiating FVIII and FXIII replacement therapy, cranioplasty was performed without further bleeding. The patient recovered with minimal neurological deficits and remains functionally independent. This case underscores the need to consider undiagnosed congenital hemophilia in elderly patients with recurrent ASDH or unexplained postoperative rebleeding. Early, targeted coagulation studies, including FVIII and FXIII assays, are critical for diagnosis. Our findings suggest that even mild FXIII deficiency may exacerbate bleeding in hemophilia A, highlighting the limitations of routine coagulation tests. Adequate perioperative replacement of FVIII and FXIII can support safe neurosurgical outcomes.