Introduction
Hereditary interstitial lung disease (HILD) associated with surfactant protein C gene (SFTPC ) variation exhibits various phenotypes, including asymptomatic adults or severe respiratory failure in infancy.1 Although several case reports have shown success with hydroxychloroquine (HCQ) treatment, other factors that can predict treatment responsiveness or disease prognosis remain largely unknown. Improvement of oxygenation was often used as a clinical parameter,2 but it is difficult to evaluate the oxygenation under specific oxygen concentrations when using conventional oxygen therapy in young children.3 Especially for patients with HILD, the oxygen concentration via a nasal cannula can vary due to respiratory distress. Here, we report that a high-flow nasal cannula (HFNC) was useful for clinical evaluation in the case of HILD with SFTPC variation.