FRIDAY, April 3 (HealthDay News) -- A defective gene, a long car ride, a daily contraceptive dose and grapefruit for breakfast added up to a limb-threatening medical emergency for a woman in a case reported in the April 4 issue of The Lancet.

Lucinda A Grande, M.D., of St. Peter Hospital in Olympia, Wash., and colleagues report on the case of a 42-year-old woman who limped into the emergency department with a badly swollen and bluish left leg and signs of phlegmasia caerulea dolens threatening gangrene. Immediate ultrasound revealed a deep vein thrombosis extending from the external iliac vein distal to the calf. Emergency personnel began intravenous heparin, and surgeons quickly performed catheter-directed thrombolysis using recombinant tissue plasminogen activator. Radiography revealed a stenosis in the left common iliac vein, and a stent was placed.

By evening, the swelling had gone down and normal color had returned to the woman's leg, the authors note. With further study, it was determined the woman had factor V Leiden mutation (a hypercoagulability disorder) and was taking an estrogen contraceptive, which also increases blood coagulability. Physicians theorized that sitting in the car for 90 minutes the previous day crimped the blood vessel, and the grapefruit the woman had been eating as part of a new diet augmented the action of the ethinylestradiol in the contraceptive by inhibiting the enzyme CYP3A4, further increasing coagulability.

"Our patient had a constellation of potential risk factors for venous thrombosis; a heightened hypercoagulable state from increased ethinylestradiol serum concentration due to her three days of grapefruit for breakfast may well have tipped the balance," the authors write.

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