Unmasking Factor XIII Deficiency: Recurrent Intracranial Hemorrhage Despite Normal Coagulation Studies.

Factor XIII (FXIII) deficiency is a rare bleeding disorder that can be easily missed because routine coagulation tests remain normal. We report a 32-year-old Nicaraguan man who carried a childhood diagnosis of von Willebrand disease and was inadvertently managed with cryoprecipitate for 25 years, a treatment that incidentally corrected his true underlying deficiency due to its high FXIII content. After immigrating and transitioning to von Willebrand factor/Factor VIII concentrate, he developed recurrent life-threatening intracranial hemorrhages. FXIII activity testing ultimately revealed a level of less than 5%, confirming severe FXIII deficiency. He was started on FXIII concentrate prophylaxis with no further bleeding events. This case highlights how diagnostic anchoring and inadvertent treatment with cryoprecipitate can mask FXIII deficiency for decades. Furthermore, it underscores the importance of considering FXIII testing in patients with severe or recurrent bleeding and normal standard coagulation studies.