A young woman presents with a history of recurrent deep vein thrombosis presents with shortness of breath.

A 24-year-old nulliparous female with a history of recurrent deep vein thrombosis presents with shortness of breath.
The full blood count and clotting screen reveals the following results:
Hb 12.4 g/dl
Plateltes 137 WBC 7.5 * 109/l
PT 14 secs
APTT 46 secs

What is the most likely underlying diagnosis?
A. Third generation oral contraceptive pill use
B. Protein C deficiency
C. Antithrombin III deficiency
D. Antiphospholipid syndrome
E. Activated protein C resistance

Answer: D. Antiphospholipid syndrome

Discussion: The combination of a prolonged APTT and thrombocytopenia make antiphospholipid syndrome the most likely diagnosis.

Antiphospholipid syndrome

Antiphospholipid syndrome is an acquired disorder characterised by a predisposition to both venous and arterial thromboses, recurrent fetal loss and thrombocytopenia. It may occur as a primary disorder or secondary to other conditions, most commonly systemic lupus erythematosus (SLE) A key point for the exam is to appreciate that antiphospholipid syndrome causes a paradoxical rise in the APTT. This is due to an ex-vivo reaction of the lupus anticoagulant autoantibodies with phospholipids involved in the coagulation cascade


Clinical Features
 venous/arterial thrombosis
 recurrent fetal loss
 livedo reticularis
 thrombocytopenia
 prolonged APTT
 other features: pre-eclampsia, pulmonary hypertension

Associations other than SLE
 other autoimmune disorders
 lymphoproliferative disorders
 phenothiazines (rare)

Management - based on BCSH guidelines
 initial venous thromboembolic events: evidence currently supports use of warfarin with a target INR of 2-3 for 6 months
 recurrent venous thromboembolic events: lifelong warfarin; if occurred whilst taking warfarin then increase target INR to 3-4
 arterial thrombosis should be treated with lifelong warfarin with target INR 2-3