# Atypical STING-Vasculopathy Phenotype: Definite Usual Interstitial Pneumonia (UIP)-Pattern CT With Mixed Fibrotic Histology: A Case Report

## TL;DR

A 20-year-old man with SAVI developed a rare lung fibrosis pattern resembling usual interstitial pneumonia, triggered by a viral infection, leading to lung transplant.

## Contribution

Reports a rare UIP-pattern CT in SAVI-associated ILD with mixed UIP-NSIP histology, highlighting acute viral decompensation.

## Key findings

- Patient with SAVI showed definite UIP-pattern CT findings despite mixed UIP-NSIP histology.
- Acute respiratory failure was triggered by respiratory syncytial virus infection.
- Lung transplant revealed fibrotic changes without definitive fibroblastic foci.

## Abstract

STING‑associated vasculopathy with onset in infancy (SAVI) is a rare autoinflammatory disorder that causes systemic inflammation, vasculopathy, and progressive interstitial lung disease (ILD). The pulmonary manifestations of SAVI typically resemble a nonspecific interstitial pneumonia (NSIP) pattern both radiologically and histologically. We present a case of a 20‑year‑old male with genetically confirmed SAVI who developed acute hypoxic respiratory failure triggered by respiratory syncytial virus infection, despite appropriate treatment. Imaging revealed extensive subpleural fibrosis, traction bronchiectasis, and honeycombing. These findings were observed in the setting of a CT appearance strongly consistent with a definite usual interstitial pneumonia (UIP) pattern. Ultimately, the patient underwent a lung transplant, and histopathology of the explanted lungs revealed fibrotic changes, including diffuse interstitial thickening, lymphoid aggregates, and honeycombing, without definitive fibroblastic foci, indicating a mixed UIP and NSIP pattern of fibrosis. This case illustrates a rare UIP‑pattern imaging phenotype in SAVI‑associated ILD, despite a mixed UIP‑NSIP histologic pattern of pulmonary fibrosis, and highlights the potential for acute viral infection to precipitate decompensation in patients with interferon‑driven pulmonary fibrosis.

Written informed consent was obtained from the patient for publication of this report and accompanying images.