Diffuse microvascular pulmonary thrombosis associated with primary antiphospholipid antibody syndrome.

Thromboembolism is a well-known complication of the hypercoagulable state associated with antiphospholipid (aPL) antibodies. Acute respiratory failure (ARF) with diffuse pulmonary infiltrates has been reported in only a few patients with aPL antibodies. We describe a 49 year old patient with spiking fever, livedo reticularis, mild haemoptysis and ARF. Chest radiography revealed diffuse bilateral pulmonary infiltrates, and high resolution computed tomography (CT) revealed patchy distribution of areas of ground-glass attenuations. Pulmonary emboli were excluded with angiography. Lung biopsy revealed diffuse microvascular thrombosis, without capillaritis. High serum levels of anticardiolipin (aCL) antibodies were found. The patient's condition improved dramatically after intravenous infection of 1 g methylprednisolone on three consecutive days, followed by 50 mg prednisone orally. The rapid improvement following the administration of glucocorticosteroids suggests that anticardiolipin associated microvascular thrombosis, without inflammatory lesions, may depend on an interference with beta2-glycoprotein I (beta2=GPI) by anticardiolipin.