The great deception: tranexamic acid and extensive pulmonary emboli.

Pulmonary embolism (PE) is a common and life-threatening condition. The British Thoracic Society PE guidelines state that PE is reliably excluded in patients with low-intermediate clinical probability and a negative D-dimer. We are reporting the case of a 47-year-old lady, taking tranexamic acid for menorrhagia, who presented with shortness of breath and was diagnosed with extensive bilateral PE. She had a low clinical risk of PE as determined by her Wells score, and a subsequent negative D-dimer. This patient's D-dimer value of 15 ng/ml (HemosIL DD HS assay) was the lowest associated with any CT pulmonary angiogram (n=1645) recorded at our trust over a 2-year period. This lady was successfully treated with a heparin infusion and warfarin. No further thromboembolic events had occurred by 18-month follow-up. To our knowledge, this is the first case report to describe tranexamic acid causing an extremely low false-negative D-dimer masking PE.