Extensive phenotyping of individuals at risk for familial interstitial pneumonia reveals clues to the pathogenesis of interstitial lung disease.

RATIONALE: Asymptomatic relatives of patients with familial interstitial pneumonia (FIP), the inherited form of idiopathic interstitial pneumonia, carry increased risk for developing interstitial lung disease. OBJECTIVES: Studying these at-risk individuals provides a unique opportunity to investigate early stages of FIP pathogenesis and develop predictive models of disease onset. METHODS: Seventy-five asymptomatic first-degree relatives of FIP patients (mean age, 50.8 yr) underwent blood sampling and high-resolution chest computed tomography (HRCT) scanning in an ongoing cohort study; 72 consented to bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsies. Twenty-seven healthy individuals were used as control subjects. MEASUREMENTS AND MAIN RESULTS: Eleven of 75 at-risk subjects (14%) had evidence of interstitial changes by HRCT, whereas 35.2% had abnormalities on transbronchial biopsies. No differences were noted in inflammatory cells in BAL between at-risk individuals and control subjects. At-risk subjects had increased herpesvirus DNA in cell-free BAL and evidence of herpesvirus antigen expression in alveolar epithelial cells (AECs), which correlated with expression of endoplasmic reticulum stress markers in AECs. Peripheral blood mononuclear cell and AEC telomere length were shorter in at-risk individuals than healthy control subjects. The minor allele frequency of the Muc5B rs35705950 promoter polymorphism was increased in at-risk subjects. Levels of several plasma biomarkers differed between at-risk subjects and control subjects, and correlated with abnormal HRCT scans. CONCLUSIONS: Evidence of lung parenchymal remodeling and epithelial dysfunction was identified in asymptomatic individuals at risk for FIP. Together, these findings offer new insights into the early pathogenesis of idiopathic interstitial pneumonia and provide an ongoing opportunity to characterize presymptomatic abnormalities that predict progression to clinical disease.

Rare variants in RTEL1 are associated with familial interstitial pneumonia.

RATIONALE: Up to 20% of cases of idiopathic interstitial pneumonia cluster in families, comprising the syndrome of familial interstitial pneumonia (FIP); however, the genetic basis of FIP remains uncertain in most families. OBJECTIVES: To determine if new disease-causing rare genetic variants could be identified using whole-exome sequencing of affected members from FIP families, providing additional insights into disease pathogenesis. METHODS: Affected subjects from 25 kindreds were selected from an ongoing FIP registry for whole-exome sequencing from genomic DNA. Candidate rare variants were confirmed by Sanger sequencing, and cosegregation analysis was performed in families, followed by additional sequencing of affected individuals from another 163 kindreds. MEASUREMENTS AND MAIN RESULTS: We identified a potentially damaging rare variant in the gene encoding for regulator of telomere elongation helicase 1 (RTEL1) that segregated with disease and was associated with very short telomeres in peripheral blood mononuclear cells in 1 of 25 families in our original whole-exome sequencing cohort. Evaluation of affected individuals in 163 additional kindreds revealed another eight families (4.7%) with heterozygous rare variants in RTEL1 that segregated with clinical FIP. Probands and unaffected carriers of these rare variants had short telomeres (<10% for age) in peripheral blood mononuclear cells and increased T-circle formation, suggesting impaired RTEL1 function. CONCLUSIONS: Rare loss-of-function variants in RTEL1 represent a newly defined genetic predisposition for FIP, supporting the importance of telomere-related pathways in pulmonary fibrosis.

Growth trajectories and oxygen use in neuroendocrine cell hyperplasia of infancy.

RATIONALE: Neuroendocrine cell hyperplasia of infancy (NEHI) typically presents in infancy with tachypnea, retractions, and hypoxemia. Some infants have failure to thrive, yet the frequency of this and other non-respiratory phenotypic features have not been delineated. While gradual improvement occurs, the clinical course is variable and the duration of supplemental oxygen requirement has not been defined. OBJECTIVES: Our objective was to identify factors in NEHI that may drive differences in clinical course. We hypothesized that failure to thrive would be associated with greater duration of supplemental oxygen use. METHODS: Children with NEHI were identified as a nested retrospective cohort within an ongoing observational prospective study. An electronic questionnaire evaluating health status was distributed to the parents/guardians. Clinical data were obtained via chart review and parent interview. RESULTS: Of 42 children, 74% had a diagnosis of failure to thrive during their clinical course. Time to event analysis demonstrated that 50% discontinued daytime and nighttime oxygen at 32 and 87.5 months after initiation, respectively. Diagnosis of failure to thrive was associated with longer continuous oxygen supplementation, P = 0.03. Additional parental concerns identified through the electronic questionnaire included developmental delays, multiple hospitalizations, and delays in diagnosis. CONCLUSIONS: NEHI is associated with substantial respiratory and extra-pulmonary morbidity. Failure to thrive may be associated with greater respiratory morbidity, though further studies are required to define this interaction. Determining the association of these comorbidities and respiratory course in NEHI may enable development of strategies to improve these modifiable factors and potentially pulmonary outcomes.

Persistent Lung Disease in Adults with NKX2.1 Mutation and Familial Neuroendocrine Cell Hyperplasia of Infancy.

RATIONALE: Neuroendocrine cell hyperplasia of infancy (NEHI) is a diffuse lung disease that presents in infancy and improves during childhood. Long-term outcomes have not previously been described. In one familial cohort, we have reported that NEHI is associated with a heterozygous variant of NKX2.1/TTF1. OBJECTIVES: Our objective was to determine whether pulmonary abnormalities persist in adults with NEHI, to aid in elucidating the natural history of this disease. METHODS: Four adult relatives with heterozygous NKX2.1 mutation and with clinical histories compatible with NEHI enrolled in a prospective study that included questionnaires, pulmonary function tests, and chest computed tomography scans. MEASUREMENTS AND MAIN RESULTS: Mild radiologic abnormalities including mosaicism were seen in all four cases. Three individuals had obstruction on pulmonary function tests, two had marked air trapping, and three had symptomatic impairments with exercise intolerance. CONCLUSIONS: Although clinical improvement occurs over time, NEHI may result in lifelong pulmonary abnormalities in some cases. Further studies are required to better describe the natural history of this disease and would be facilitated by additional delineation of genetic mechanisms to enable improved case identification.