ObjectiveTo detect the pulmonary involvement in asymptomatic secondary APS patients by pulmonary function tests (PFTs) and chest multislice HRCT angiography. Comparing the pulmonary findings to those of asymptomatic SLE patients without APS was considered. Patients and methodsThirty-four SLE patients with APS and another 34 SLE patients without APS and with a negative ACL test were included as control. All patients were asymptomatic for any pulmonary manifestations. Plain chest X-ray, HRCT angiography and PFTs were performed for all patients in an attempt to assess the pulmonary vasculature and lung parenchyma. Disease activity was assessed using the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) while assessment of organ damage was made using the Systemic Lupus International Collaborating Clinics/ACR (SLICC/ACR) index. ResultsThere were abnormal pulmonary CT findings in 11 (32.35%) of the asymptomatic secondary APS patients with an obvious association to lupus anticoagulants. However, plain X-ray showed basal atelectasis and/or elevation of the copulae in four patients. Pulmonary abnormalities included a high frequency of pulmonary artery aneurysms (20.59%) thrombosis, basal atelectasis, embolism, bronchiectasis, pleural effusion and thickening. The SLEDAI and SLICC were significantly higher in APS patients. More SLE patients without APS were receiving hydroxychloroquine which suggests a protective role on the thromboembolic events occurring in APS. ConclusionMultislice HRCT pulmonary angiography, with its multiplanar capability, vascular reconstruction and high quality, is useful in demonstrating the entire thoracic spectrum in asymptomatic APS patients. Particular concern about the medications used in APS could prevent the risk of developing noticeable thromboembolic events.