A 49 year old white man presented with extensive deep vein thrombosis and reported a number of recent transcient ischaemic episodes. He was diagnosed three years previously with primary antiphospholipid antibody syndrome (APS), having had an ischaemic episode, raised anticardiolipin antibodies (IgG aCL 37 u/ml, normal <20), absence of clinical or serological evidence of systemic lupus erythematosus, etc, and was taking aspirin 75 mg daily. He also had an IgM κ paraprotein (5.3 g/l). On this occasion, IgG aCL was at the upper limit of normal, lupus anticoagulant was present (dilute Russel viper venom ratio 1.67, normal 0.81–1.19). Thrombophilia screen, including functional protein C and free protein S, was otherwise normal. Initially heparinised, he was started with warfarin treatment, target international normalised ratio (INR) 3.0 to 3.5. Three weeks later, he developed chest/flank pain and dyspnoea (pO2 7.96 kPa, pCO2 3.83 kPa, pH 7.46), severe thrombocytopenia (15 × 10⁹/l), raised …