Ultrasonic humidifier lung as a mimic of COVID‐19

Ro, Shosei; Imai, Ryosuke; Kitamura, Atsushi; Jinta, Torahiko; Nishimura, Naoki

Chest computed tomography (CT) has been used to complement coronavirus disease 2019 (COVID‐19) diagnosis due to its high sensitivity. However, owing to the low specificity of CT findings, differential diagnosis is essential. The typical CT findings of COVID‐19 include ground‐glass opacifications and consolidations with predominant distribution in bilateral, peripheral, and subpleural parts of the lung. These imaging findings are non‐specific and may resemble other lung conditions, including ultrasonic humidifier lung, which is a condition that develops on inhaling aerosols generated by ultrasonic humidifiers. We present two patients with initial symptoms similar to COVID‐19. CT examination revealed centrilobular nodules and consolidations with upper lobe‐predominant distribution, although atypical for COVID‐19, but key findings for ultrasonic humidifier lung. Therefore, ultrasonic humidifier lung could be a differential diagnosis for COVID‐19 in dry environments. Characteristic CT findings and a history of ultrasonic humidifier use are critical to the final diagnosis.