Hypersensitivity pneumonitis with Paecilomyces as suspected inciting antigen

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.