Cigarette smoking and pulmonary diffusion defects in rheumatoid arthritis

A novel humanized model of rheumatoid arthritis associated lung disease

Cigarette smoking has been implicated in the pathogenesis of seropositive rheumatoid arthritis (RA), as well as RA-associated lung disease. Fibrotic interstitial lung disease as well as emphysema occur in RA and cause substantial morbidity. We used arthritis-susceptible HLA-DQ8 transgenic mice to generate RA-associated lung disease. Mice were exposed to cigarette smoke (CS) prior to induction of arthritis, and subsequently injected with a low dose of bleomycin intra-tracheally to induce lung injury. Exposure of arthritic mice to both CS and bleomycin led to a significant reduction in lung compliance consistent with development of diffuse lung disease. Morphologic evaluation of the lung demonstrated areas of emphysematous change and co-existent fibrosis, consistent with a combined pattern of fibrosis and emphysema. These changes were accompanied by inflammatory cell infiltration and upregulation of fibrosis-associated genes. This humanized mouse model can serve as a valuable research tool to understand the pathogenesis of RA associated lung disease.

Smoking and Subclinical ILD in RA versus the Multi-Ethnic Study of Atherosclerosis

A population-based cohort showed an association between cigarette smoking and subclinical parenchymal lung disease defined as regions of increased computed tomography (CT) lung densitometry. This technique has not been applied to the rheumatoid arthritis (RA) population where associated ILD is highly prevalent. The association between cumulative cigarette smoking and volume of areas of high attenuation (HAA: >-600 and <-250 Hounsfield Units) on full inspiratory CT was compared in 172 RA participants and 3,969 controls in a general population sample. Multivariable regression models were used to adjust for demography, anthropometrics, percent emphysema, and CT parameters. The mean cumulative cigarette smoking exposure was 25 (IQR 10–42) and 15(IQR 5–31) pack-years for the RA and non-RA cohorts, respectively. Mean HAA was 153(±57) cm³ and 129(±50) cm³ in the RA and non-RA cohorts, respectively. Each 10 cigarette pack-year increment was associated with a higher HAA by 0.03% (95% CI, 0.007–0.05%) in RA patients and by 0.008% (95% CI, 0.003–0.01%) in those without RA (interaction p = 0.001). Cigarette smoking was associated with higher lung attenuation; with a magnitude of association more pronounced in those with RA than in the general population. These data suggest that cigarette smoking may be a more potent ILD risk factor for RA patients than in the general population.

The multifaceted aspects of interstitial lung disease in rheumatoid arthritis

Interstitial lung disease (ILD) is a relevant extra-articular manifestation of rheumatoid arthritis (RA) that may occur either in early stages or as a complication of long-standing disease. RA related ILD (RA-ILD) significantly influences the quoad vitam prognosis of these patients. Several histopathological patterns of RA-ILD have been described: usual interstitial pneumonia (UIP) is the most frequent one, followed by nonspecific interstitial pneumonia (NSIP); other patterns are less commonly observed. Several factors have been associated with an increased risk of developing RA-ILD. The genetic background plays a fundamental but not sufficient role; smoking is an independent predictor of ILD, and a correlation with the presence of rheumatoid factor and anti-cyclic citrullinated peptide antibodies has also been reported. Moreover, both exnovo occurrence and progression of ILD have been related to drug therapies that are commonly prescribed in RA, such as methotrexate, leflunomide, anti-TNF alpha agents, and rituximab. A greater understanding of the disease process is necessary in order to improve the therapeutic approach to ILD and RA itself and to reduce the burden of this severe extra-articular manifestation.

Histopathologic Pattern and Clinical Features of Rheumatoid Arthritis-Associated Interstitial Lung Disease

STUDY OBJECTIVES

To investigate the histopathologic pattern and clinical features of patients with rheumatoid arthritis (RA)-associated interstitial lung disease (ILD) according to the American Thoracic Society (ATS)/European Respiratory Society consensus classification of idiopathic interstitial pneumonia.

DESIGN

Retrospective review.

SETTING

Two thousand-bed, university-affiliated, tertiary referral center.

PATIENTS

Eighteen patients with RA who underwent surgical lung biopsy (SLBx) for suspected ILD.

METHOD

SLBx specimens were reviewed and reclassified by three lung pathologists according to the ATS/European Respiratory Society classification. Clinical features and follow-up courses for the usual interstitial pneumonia (UIP) pattern and the nonspecific interstitial pneumonia (NSIP) pattern were compared.

RESULTS

The histopathologic patterns were diverse: 10 patients with the UIP pattern, 6 patients with the NSIP pattern, and 2 patients with inflammatory airway disease with the organizing pneumonia pattern. RA preceded ILD in the majority of patients (n = 12). In three patients, ILD preceded RA; in three patients, both conditions were diagnosed simultaneously. The majority (n = 13) of patients had a restrictive defect with or without low diffusion capacity of the lung for carbon monoxide (D(LCO)) on pulmonary function testing; 2 patients had only low (D(LCO)). The UIP and NSIP groups were significantly different in their male/female ratios (8/2 vs 0/6, respectively; p = 0.007) and smoking history (current/former or nonsmokers, 8/2 vs 0/6; p = 0.007). Many of the patients with the UIP pattern had typical high-resolution CT features of UIP. Five patients with the UIP pattern died, whereas no deaths occurred among patients with the NSIP pattern during median follow-up durations of 4.2 years and 3.7 years, respectively.

CONCLUSIONS

The histopathologic type of RA-ILD was diverse; in our study population, the UIP pattern seemed to be more prevalent than the NSIP pattern.

Pulmonary function tests in interstitial lung disease: what role do they have?

Pulmonary function tests have been widely accepted and utilized in the management of interstitial lung diseases. Although the tests performed have changed little over the past several decades, extensive literature has been published highlighting their clinical role in the diagnosis, staging, prognostication, and follow-up of patients with a wide variety of interstitial lung diseases.

Smoking-related interstitial lung diseases

Interstitial lung diseases (ILDs) encompass diverse clinicopathological disease entities ranging from idiopathic interstitial pneumonia (IIP) to interstitial pneumonia accompanied by collagen vascular diseases and diseases related to smoking, drug reactions, occupational environments, infections, and malignancies. Our focus is on the smoking-related interstitial lung diseases. Specifically, we focus on reports suggesting that chronic smoking is deeply involved in the disease pathogenesis and on reports suggesting that chronic smoking may influence the clinical course in terms of either disease severity or progression. Pulmonary Langerhans' cell granulomatosis (PLCG), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis with interstitial lung diseases (RB-ILD), interstitial pneumonia associated with rheumatoid arthritis, acute respiratory distress syndrome (ARDS), and idiopathic pulmonary fibrosis (IPF) are covered.