Thrombosis in rare bleeding disorders: a bleeding phenotype does not fully preclude thrombotic risk- frequency, clinical contexts, and management in a large Iranian cohort.
Imaging-confirmed thrombosis occurred in about 1% of rare bleeding disorder patients.
Thrombosis in rare bleeding disorders: a bleeding phenotype does not fully preclude thrombotic risk- frequency, clinical contexts, and management in a large Iranian cohort.
Bleeding is the dominant clinical feature of rare bleeding disorders (rare bleeding disorders), yet thrombotic events have occasionally been reported.
We aimed to estimate the frequency of imaging-confirmed thrombosis and describe associated clinical contexts and potential predisposing factors in an unselected rare bleeding disorders cohort.
This single-center retrospective study was conducted on all patients with confirmed diagnoses of rare bleeding disorders, including rare coagulation factor deficiencies, von Willebrand disease, and inherited platelet function disorders, under care at our center between January and December 2025.
thrombosis was rare, and almost always tied to pregnancy, surgery, or infection
Events were exclusively venous.
Events occurred mainly as deep vein thrombosis (50%) or cerebral venous thrombosis (41.7%), with other sites less common, most often in high-risk contexts such as pregnancy (4 cases), surgery, infection, or exposure to prothrombin complex concentrate (prothrombin complex concentrate).
Thrombosis was more frequent in afibrinogenemia (7.1%) and FII deficiency (8.3%) than in FXIII deficiency (0.7%), although interpretation is limited by small numbers.
In a sensitivity analysis excluding events associated with pregnancy, surgery, and exposure prothrombin complex concentrate, the proportion decreased to 0.48% (6/1,251; 95% CI, 0.18-1.04%).
Thrombosis in rare bleeding disorders was rare and largely associated with major transient high-risk contexts and/or treatment exposure.
Prospective multicenter studies are needed to improve the evidence base for clinical decision making regarding thrombotic risks in this vulnerable population.