Abstract Familial idiopathic interstitial pneumonia (FPF) is defined as the occurrence of interstitial pneumonia in two or more members of the same biological family. Approximately 150 such families have been reported worldwide, predominantly in Europe and North America, but data from the Philippines remain scarce. Studying affected family members provides valuable insight into the early pathogenesis of idiopathic pulmonary fibrosis (IPF), particularly during stages when treatment may still modify disease progression. Here, we describe four related cases of FPF identified after a comprehensive family history assessment. A 72-year-old woman, non-smoker, presented with one-year history of progressive dyspnea and cough. Examination revealed bibasilar end-inspiratory crackles. Pulmonary function testing (PFT) and a six-minute walk test (6MWT) showed a moderate restrictive defect, able to walk 149m and severe desaturation to 74% despite 5 L/min oxygen supplementation. Serologic tests for connective tissue disease were negative. Chest high-resolution computed tomography (HRCT) demonstrated extensive reticular and fibrotic densities with traction bronchiectasis and honeycombing, predominantly in the peripheral and basal regions, consistent with interstitial lung disease (ILD) showing a usual interstitial pneumonia (UIP) pattern. She was started on triple angiokinase inhibitor therapy and enrolled in pulmonary rehabilitation, with noted clinical improvement. Her daughter, who died of a pulmonary cause, had also presented with progressive dyspnea and pneumothorax; HRCT findings had shown ILD with a UIP pattern. A 63-year-old woman, also a non-smoker and first-degree cousin of the index patient, presented with one year of progressive shortness of breath, easy fatigability and cough. Physical findings and PFT results were similar, showing a moderate restrictive defect, able to walk 192m and desaturation to 84% on 4 L/min oxygen. Autoimmune and collagen vascular serologies were negative, and HRCT revealed ILD with UIP pattern. She was likewise started on triple angiokinase inhibitor therapy with clinical improvement. Her sister had previously died of a pulmonary cause, presented with progressive dyspnea and cough; HRCT findings were consistent with ILD, UIP pattern. FPF is an uncommon and often under-recognized subset of ILD. Early recognition of familial clustering enables screening of asymptomatic relatives, detection of subclinical disease, and potential early intervention. This case series adds to the limited data on FPF among Filipinos and reporting such familial occurrence broadens global understanding of ILD and underscores the importance of detailed family history in the evaluation of patients with IPF. This abstract is funded by: None
Bangcaya et al. (Fri,) studied this question.