# Hypersensitivity pneumonitis with Paecilomyces as suspected inciting antigen

## TL;DR

An elderly man was diagnosed with hypersensitivity pneumonitis caused by Paecilomyces, a rare mold found in his home.

## Contribution

This case highlights the importance of identifying Paecilomyces as a rare inciting antigen in hypersensitivity pneumonitis.

## Key findings

- The patient's symptoms and test results improved after avoiding the antigen.
- Paecilomyces was cultured from the patient's home environment.
- Systematic approaches are crucial for diagnosing rare antigen-induced hypersensitivity pneumonitis.

## Abstract

A 73-year-old man visited our hospital for persistent cough. Chest high-resolution CT (HRCT) showed infiltration shadows in lower lobes and diffuse ground glass opacities in the upper lobes. Blood tests showed elevated white blood cell, C-reactive protein, surfactant protein D, and Krebs von den Lungen-6 levels. After an antigen avoidance test, his HRCT and blood test findings improved; we diagnosed him with hypersensitivity pneumonitis (HP). A culture of the rotting interior walls within his home revealed Paecilomyces, which we believe caused his HP. Given the few patients with Paecilomyces-induced HP, systematic approach was important to identify the inciting antigen.