Anatomic distribution of venous thrombosis in patients with antiphospholipid antibody: imaging findings

Antiphospholipid antibodies are immunoglobulins that cross-react with phospholipid within cell membranes. These antibodies have been associated with a hypercoagulable state manifested by early stroke, frequent arterial and venous thromboses, recurrent fetal loss, thrombocytopenia, and livedo reticularis (antiphospholipid syndrome). The purpose of this study was to determine the anatomic distribution of venous thrombosis in patients with antiphospholipid antibodies as seen on imaging examinations.

We retrospectively reviewed the laboratory results of patients tested for antiphospholipid antibodies at a tertiary referral center during the period January 1992 to April 1994. This review revealed 228 patients with antiphospholipid antibodies. We excluded patients with systemic lupus erythematosus or any other medical condition associated with a hypercoagulable state and patients over 65 years old. Thirty-one of the remaining 73 patients had undergone imaging studies of the CNS or non-CNS venous system. Radiologic studies (contrast angiography or venography, MR angiography or venography, or Doppler sonography) were examined for the presence of venous thrombosis. Nineteen patients--11 men and eight women, 18-62 years old (average age, 38 years)--with venous thromboses were identified.

Twelve patients had non-CNS thrombosis alone, three had CNS thrombosis alone, and four had both CNS and non-CNS thromboses. Locations of non-CNS thromboses included deep veins of the legs (nine occurrences), pulmonary vessels (five), and large veins in the thorax or abdomen (six). Three of these patients had documented thromboses at other sites. Twelve patients had recurrent thrombotic events (six with multiple recurrences), including five with arterial thromboses and two with both venous and arterial thromboses and stroke. Among patients with CNS involvement, five had documented thromboses (four dural sinus, one arterial) and two had arterial distribution strokes demonstrated by CT. Two patients with only non-CNS thromboses had either seizures or migraines.

Deep veins of the leg were the most common site of venous thrombosis. The thoracic and abdominal venous system and the dural sinuses--unusual sites of thrombosis in the general population--are other common sites. Antiphospholipid antibodies should be suspected when thromboses are found in these locations in the absence of other known risk factors, or when found in combination with arterial thromboses or CNS ischemic disease in young or middle-aged patients.