A 27-year-old man developed pain in his right calf associated with swelling of the foot. He had recently returned from New Zealand and had undertaken a 12-hour flight from Singapore to London. He was a non-smoker. He was otherwise in generally very good health.
On specific questioning, he revealed that his mother and father were well, although his father had suffered deep vein thrombosis on two occasions. He had two brothers and a sister and his sister had suffered a deep vein thrombosis soon after starting treatment with the contraceptive pill.
He was not on any medication.
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(a) What is the differential diagnosis?
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Correct answer: He is likely to have a deep vein thrombosis in his right calf. He may have a ruptured Baker cyst in the right knee, or he could have suffered a sprain or injury to his right leg.
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(b) What tests would you perform?
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Correct answer: He should undergo a Doppler ultrasound of the veins of the right leg to assess venous flow. He should also have blood tests done in preparation for the commencement of anticoagulation treatment, e.g. full blood count, biochemistry to include liver and kidney function, baseline coagulation tests.
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(c) What is the relevance of his family history?
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Correct answer: The strong family history of venous thrombosis suggests there may be an inherited thrombophilia in the family. He should undergo screening tests as discussed in Chapter 44 (Box 44.2). Specific conditions that must be excluded include the presence of factor V Leiden, antithrombin deficiency, prothrombin mutations, protein C and protein S deficiency. This patient was found to be heterozygous for factor V Leiden. Activated factor V Leiden is relatively resistant to inactivation by protein C. The risk of thrombosis is increased by 5- to 10-fold in heterozygotes and 50–100-fold in homozygotes. Up to 5% of the northern European population are heterozygous for this mutation. He was found to be heterozygous for factor V Leiden and the same abnormality was confirmed in other family members.
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(d) What complications can occur?
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Correct answer: The thrombosis in his right calf will organize if left untreated and extend. The risk of pulmonary embolism from an isolated calf thrombosis is small but increases if he is left untreated. There is a long-term risk of chronic venous insufficiency in the leg with skin discoloration, pain, swelling and discomfort.
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(e) What treatment would you undertake?
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Correct answer: He should be offered anticoagulation with once daily subcutanaeous low molecular weight heparin injections and oral warfarin should be commenced. Once the warfarin is well stabilized in a therapeutic range (INR 2–3) the heparin can be stopped. The warfarin should be continued for 6 months and he should be given a card indicating that he has factor V Leiden and is at increased risk of venous thrombosis. Every effort must be taken to reduce other risk factors for thrombosis, e.g. smoking, being overweight, taking particular care at times of haemostasis, e.g. prophylaxis with heparin prior to a intercontinental flight. He should take a prophylactic heparin injection prior to future long haul flights. If he develops a further thrombosis, he is a candidate for indefinite anticoagulation therapy. Elasticated stockings for the right leg are indicated to reduce the risk of a post thrombotic syndrome. This should be worn during the day for 1–2 years and when flying.
