Factor XIII Deficiency: A Rare Cause of Hydrocephalus in Infancy.

Factor XIII deficiency is a very rare bleeding disorder that can cause serious bleeding problems, especially in infants. We describe a 5-month-old girl who came in with a rapidly increasing head size and a bulging fontanelle. She had no fever or injury. A CT scan showed bleeding in the right side of her brain and hydrocephalus. Her factor XIII level was low, about 25%, while other clotting factors were normal. Her older brother had the same condition and unfortunately died at 9 months due to similar brain bleeding and infection. She was treated with plasma products to replace the missing factor, antibiotics, and seizure medications. After treatment, her condition improved and she was discharged with plans for close follow-up. This case shows how factor XIII deficiency can lead to life-threatening bleeding and hydrocephalus. Early diagnosis and treatment are crucial, and knowing the family history was important here. She will need ongoing monitoring to catch any future bleeding or complications early.