Antiphospholipid Syndrome Mimicking Acute Exacerbation of Interstitial Pneumonia: A Case Report and Literature Review.

Acute exacerbation of interstitial pneumonia (IP-AE) is a type of severe respiratory failure that occurs in patients with chronic interstitial pneumonia. Herein, we report a case of multiple pulmonary thrombi caused by antiphospholipid antibody syndrome (APS), which required differentiation from IP-AE in a patient with chronic interstitial pneumonia. A 77-year-old male patient presented with acute respiratory failure and bilateral ground-glass opacities on chest computed tomography (CT), which initially indicated IP-AE. However, the contrast-enhanced CT scan revealed multiple pulmonary thrombi, and the laboratory examination showed positivity for antiphospholipid antibodies. The patient was diagnosed with APS and was successfully treated with anticoagulant therapy and systemic corticosteroids. The pulmonary manifestations of APS may mimic those of IP-AE and may be under-recognised. Thus, APS should be considered in the differential diagnosis of acute respiratory deterioration in patients with interstitial pneumonia.