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Interstitial lung disease (ILD) remains a cause of significant morbidity and mortality in patients with connective tissue disease (CTD)-associated ILD. While some patients meet clear classification criteria for a systemic rheumatic disease, a subset of patients do not meet classification criteria but still benefit from immunosuppressive therapy. In 2015, the American Thoracic Society and European Respiratory Society described classification criteria for interstitial pneumonia with autoimmune features (IPAF) to identify patients with lung-predominant CTD who lack sufficient features of a systemic rheumatic disease to meet classification criteria. Although these criteria are imperfect, they are an important attempt to classify the patient with undifferentiated disease for future study. Rheumatologists play a key role in the evaluation of potential IPAF in patients, especially as many patients with a myositis-spectrum disease (e.g., non-Jo-1 antisynthetase syndrome, anti-melanoma differentiation-associated protein 5 antibody inflammatory myositis, or anti-PM/Scl antibody-associated inflammatory myositis) would be classified under IPAF using the currently available criteria for inflammatory myositis, and would therefore benefit from rheumatologic comanagement. The aim of this review was to describe the historical context that led to the development of these criteria and to discuss the limitations of the current criteria, diagnostic challenges, treatment options, and strategies for disease monitoring.
© 2018, American College of Rheumatology.
BACKGROUND - Next-generation sequencing of individuals with genetic diseases often detects candidate rare variants in numerous genes, but determining which are causal remains challenging. We hypothesized that the spatial distribution of missense variants in protein structures contains information about function and pathogenicity that can help prioritize variants of unknown significance (VUS) and elucidate the structural mechanisms leading to disease.
RESULTS - To illustrate this approach in a clinical application, we analyzed 13 candidate missense variants in regulator of telomere elongation helicase 1 (RTEL1) identified in patients with Familial Interstitial Pneumonia (FIP). We curated pathogenic and neutral RTEL1 variants from the literature and public databases. We then used homology modeling to construct a 3D structural model of RTEL1 and mapped known variants into this structure. We next developed a pathogenicity prediction algorithm based on proximity to known disease causing and neutral variants and evaluated its performance with leave-one-out cross-validation. We further validated our predictions with segregation analyses, telomere lengths, and mutagenesis data from the homologous XPD protein. Our algorithm for classifying RTEL1 VUS based on spatial proximity to pathogenic and neutral variation accurately distinguished 7 known pathogenic from 29 neutral variants (ROC AUC = 0.85) in the N-terminal domains of RTEL1. Pathogenic proximity scores were also significantly correlated with effects on ATPase activity (Pearson r = -0.65, p = 0.0004) in XPD, a related helicase. Applying the algorithm to 13 VUS identified from sequencing of RTEL1 from patients predicted five out of six disease-segregating VUS to be pathogenic. We provide structural hypotheses regarding how these mutations may disrupt RTEL1 ATPase and helicase function.
CONCLUSIONS - Spatial analysis of missense variation accurately classified candidate VUS in RTEL1 and suggests how such variants cause disease. Incorporating spatial proximity analyses into other pathogenicity prediction tools may improve accuracy for other genes and genetic diseases.
BACKGROUND - Initial reports of transbronchial cryobiopsy for diffuse parenchymal lung disease (DPLD) suggest the diagnostic yield approaches that of surgical lung biopsy (SLB) with an excellent safety profile. Centers performing cryobiopsy differ significantly in procedure technique; an optimal technique minimizing complications but still capable of diagnosing a wide range of DPLDs has not been established. We evaluated our practice of flexible bronchoscopic cryobiopsy in a primarily outpatient setting for patients who required a tissue diagnosis for DPLD of uncertain etiology.
METHODS - Consecutive patients with indeterminate DPLD who underwent bronchoscopic cryobiopsy at a large academic medical center from January 2012 to August 2015 were retrospectively analyzed. Rates of confident histopathologic diagnosis, confident multidisciplinary consensus diagnosis, management change, and complications were determined.
RESULTS - One hundred four cases were identified. Confident histopathologic diagnoses were established in 44% (46/104) and confident multidisciplinary consensus diagnoses in 68% (71/104). Usual interstitial pneumonia (19/104) and idiopathic pulmonary fibrosis (22/104) were the most common histopathologic and consensus diagnoses, respectively. Five subjects proceeded to SLB after cryobiopsy which was diagnostic in 3. Results of cryobiopsies changed management in 70% (73/104). Complications occurred in 8 cases with no death.
CONCLUSIONS - Cryobiopsy during outpatient flexible bronchoscopy facilitated confident multidisciplinary consensus diagnosis of DPLD in more than two thirds of cases, and appears sufficient to establish the histopathologic diagnosis of usual interstitial pneumonia, with a complication rate that compares favorably to that reported for SLB.
We investigated associations of plasma lipoproteins with subclinical interstitial lung disease (ILD) by measuring high attenuation areas (HAA: lung voxels between -600 and -250 Hounsfield units) in 6700 adults and serum MMP-7 and SP-A in 1216 adults age 45-84 without clinical cardiovascular disease in Multi-Ethnic Study of Atherosclerosis. In cross-sectional analyses, each SD decrement in high density lipoprotein cholesterol (HDL-C) was associated with a 2.12% HAA increment (95% CI 1.44% to 2.79%), a 3.53% MMP-7 increment (95% CI 0.93% to 6.07%) and a 6.37% SP-A increment (95% CI 1.35% to 11.13%), independent of demographics, smoking and inflammatory biomarkers. These findings support a novel hypothesis that HDL-C might influence subclinical lung injury and extracellular matrix remodelling.
Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.
BACKGROUND - Interstitial lung disease is common in patients with sickle cell anemia (SCA). Fibrocytes are circulating cells implicated in the pathogenesis of pulmonary fibrosis and airway remodeling in asthma. In this study, we tested the hypotheses that fibrocyte levels are: (1) increased in children with SCA compared to healthy controls, and (2) associated with pulmonary disease.
PROCEDURE - Cross-sectional cohort study of children with SCA who participated in the Sleep Asthma Cohort Study.
RESULTS - Fibrocyte levels were obtained from 45 children with SCA and 24 controls. Mean age of SCA cases was 14 years and 53% were female. In children with SCA, levels of circulating fibrocytes were greater than controls (P < 0.01). The fibrocytes expressed a hierarchy of chemokine receptors, with CXCR4 expressed on the majority of cells and CCR2 and CCR7 expressed on a smaller subset. Almost half of fibrocytes demonstrated α-smooth muscle actin activation. Increased fibrocyte levels were associated with a higher reticulocyte count (P = 0.03) and older age (P = 0.048) in children with SCA. However, children with increased levels of fibrocytes were not more likely to have asthma or lower percent predicted forced expiratory volume in 1 sec/forced vital capacity (FEV1 /FVC) or FEV1 than those with lower fibrocyte levels.
CONCLUSIONS - Higher levels of fibrocytes in children with SCA compared to controls may be due to hemolysis. Longitudinal studies may be able to better assess the relationship between fibrocyte level and pulmonary dysfunction.
© 2015 Wiley Periodicals, Inc.
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.