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

## TL;DR

A case of antiphospholipid antibody syndrome was mistaken for a severe lung condition, but successful treatment was achieved with anticoagulants and steroids.

## Contribution

This case highlights APS as a potential mimic of interstitial pneumonia exacerbation and presents an effective treatment approach.

## Key findings

- A 77-year-old patient with chronic interstitial pneumonia was diagnosed with APS after presenting with acute respiratory failure.
- Contrast-enhanced CT and antiphospholipid antibody testing confirmed APS, not IP-AE.
- Treatment with anticoagulants and corticosteroids led to successful recovery.

## Abstract

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.

Acute exacerbation of interstitial pneumonia (IP‐AE) is a type of severe respiratory failure that occurs in patients with chronic interstitial pneumonia. However, a few cases of lung involvement caused by antiphospholipid antibody syndrome (APS) appearing similar to IP‐AE have been reported. Here, we present a case of APS manifesting as IP‐AE in which the patient achieved a favorable outcome with initial combination therapy using corticosteroids and anticoagulants followed by maintenance anticoagulation, and provide a literature review.