Classification of idiopathic interstitial pneumonias: making sense of the alphabet soup

Demystifying idiopathic interstitial pneumonia: time for more etiology-focused nomenclature in interstitial lung disease

INTRODUCTION

A major focus of interstitial lung disease (ILD) has centered on disorders termed idiopathic interstitial pneumonias (IIPs) which include, among others, idiopathic pulmonary fibrosis, idiopathic nonspecific interstitial pneumonia, cryptogenic organizing pneumonia, and respiratory bronchiolitis-interstitial lung disease.

AREAS COVERED

We review the radiologic and histologic patterns for the nine disorders classified by multidisciplinary approach as IIP, and describe the remarkable amount of published epidemiologic, translational, and molecular studies demonstrating their associations with numerous yet definitive environmental exposures, occupational exposures, pulmonary diseases, systemic diseases, medication toxicities, and genetic variants.

EXPERT OPINION

In the 21st century, these disorders termed IIPs are rarely idiopathic, but rather are well-described radiologic and histologic patterns of lung injury that are associated with a wide array of diverse etiologies. Accordingly, the idiopathic nomenclature is misleading and confusing, and may also promote a lack of inquisitiveness, suggesting the end rather than the beginning of a thorough diagnostic process to identify ILD etiology and initiate patient-centered management. A shift toward more etiology-focused nomenclature will be beneficial to all, including patients hoping for better life quality and disease outcome, general medicine and pulmonary physicians furthering their ILD knowledge, and expert ILD clinicians and researchers who are advancing the ILD field.

Radiological and Physiological Predictors of IPF Mortality

Background and Objectives: Idiopathic pulmonary fibrosis (IPF) has a variable clinical course, which ranges from being asymptomatic to progressive respiratory failure. The purpose of this study was to evaluate the novel clinical parameters of IPF patients who receive an anti-fibrotic agent. Materials and Methods: From January 2011 to January 2021, we identified 39 IPF patients at Okinawa Chubu Hospital. Clinical information was obtained, such as laboratory data, pulmonary function test (PFT) results, and chest images, including of soft tissue thickness and the high-resolution computed tomography (HRCT) pattern at diagnosis. Results: The mean age was 72.9 ± 7.0 (53–85); 27 patients were men and 12 were women. The mean body mass index was 25.1 ± 3.9 (17.3–35). Twenty-four were active smokers and the median number of packs per year was 20. Regarding laboratory findings, mean white blood cell (WBC), lactate dehydrogenase (LDH), and Krebs Von den Lungen-6 (KL-6) values were 7816 ± 1859, 248 ± 47, and 1615 ± 1503, respectively. In PFT, the mean percent predicted FVC, percent predicted total lung capacity, percent predicted functional residual capacity (FRC), and percent predicted diffusion capacity of the lung for carbon monoxide (DLco) were 66.8 ± 14.9%, 71.8 ± 13.7%, 65 ± 39.6%, and 64.6 ± 27.9%, respectively. In chest radiological findings, soft tissue thickness at the right 9th rib was 26.4 ± 8.8 mm. Regarding chest HRCT patterns, 15 showed the definite usual interstitial pneumonia (UIP) pattern, 16 showed the probable UIP pattern, and eight showed the indeterminate for UIP pattern. In the treatment, 24 patients received pirfenidone and 15 patients took nintedanib. The mean observation period was 38.6 ± 30.6 months and 24 patients died. The median survival time was 32.4 months (0.9–142.5). Multivariate analysis adjusted for age showed that both soft tissue thickness [Hazard ratio (HR): 0.912, 95% confidence interval (CI): 0.859–0.979, p-value: 0.009] and percent FRC [HR: 0.980, 95% CI: 0.967–0.992, p-value: 0.002] were robust predictors of IPF mortality. Conclusions: In IPF patients treated with anti-fibrotic agents, both soft tissue thickness at the right 9th rib shown on the chest radiograph and %FRC can be novel predictors of IPF mortality.

Radiological images of interstitial pneumonia in mixed connective tissue disease compared with scleroderma and polymyositis/dermatomyositis

OBJECTIVE

Little has been reported on the radiological and pathological findings of interstitial pneumonia in mixed connective tissue disease (MCTD). There may be possible difference in treatment response and prognosis between the imaging patterns of systemic sclerosis (SSc)-like and polymyositis/dermatomyositis (PM/DM)-like. The purpose of this study was to examine whether the radiological images of interstitial pneumonia in MCTD presented SSc-like or PM/DM-like pattern, and to assess whether the imaging patterns corresponded to clinical and pathological features.

MATERIALS AND METHODS

This retrospective study included 29 patients with interstitial pneumonia who underwent surgical lung biopsy; 10 with SSc, 10 with PM/DM, and 9 with MCTD. High resolution computed tomography (HRCT) images were classified as SSc, PM/DM, or the other pattern by two radiologists independently without clinical information. The pathology of the lung specimens from MCTD patients were evaluated and compared with the imaging pattern.

RESULTS

The concordance rate between clinical diagnosis and radiological pattern was 100% in SSc patients, and 80% in PM/DM patients. Among patients with MCTD, imaging patterns were classified as SSc pattern in 4 (MCTD-SSc), PM/DM pattern in 4 (MCTD-PM/DM) and other in one. The imaging patterns did not always correlate with the clinical findings in MCTD patients. Pathologically, plasma cell infiltration and organizing pneumonia were relatively more frequent in MCTD-PM/DM, and smooth muscle hyperplasia was relatively more frequent in MCTD-SSc.

CONCLUSION

HRCT images in MCTD patients can be classified as SSc pattern or PM/DM pattern. MCTD-SSc and MCTD-PM/DM were corresponded to similar pathological findings of SSc and PM/DM.

Interstitial Lung Disease in West Highland White Terriers

Progressive respiratory failure and pulmonary fibrosis in West Highland White Terriers (WHWT) is an apparently genetic disorder of unknown pathogenesis. This study characterizes the light microscopic, ultrastructural, and immunohistochemical features of affected WHWT in comparison with lesions in usual interstitial pneumonia (UIP) of humans. Lesions in WHWT were confined to the expansion of the interstitial space of alveolar septa by extracellular matrix (ECM) determined to be mixtures of type-I and -III collagens. Features of UIP such as intra-alveolar fibroblastic foci, subpleural distribution, and honeycombing were not observed in six WHWT. Comparison with normal dogs showed no apparent increase in septal myofibroblasts. Ultrastructually, the ECM in alveolar septa consisted of large aggregates of periodic collagen filaments underlying alveolar capillaries that were surrounded by thick bands of amorphous to fine fibrillar matrix. This study suggests that chronic pulmonary disease of WHWT is a result of aberrant collagen regulation.

Imaging of pulmonary involvement in rheumatic disease

Lung disease commonly occurs in connective tissue diseases (CTD) and is an important cause of morbidity and mortality. Imaging is central to the evaluation of CTD-associated pulmonary complications. In this article, a general discussion of radiologic considerations is followed by a description of the pulmonary appearances in individual CTDs, and the imaging appearances of acute and nonacute pulmonary complications. The contribution of imaging to monitoring disease, evaluating treatment response, and prognostication is reviewed. Finally, we address the role of imaging in the challenging multidisciplinary evaluation of interstitial lung disease where there is an underlying suspicion of an undiagnosed CTD.

Experimental induction of pulmonary fibrosis in horses with the gammaherpesvirus equine herpesvirus 5

Gammaherpesviruses (γHV) are implicated in the pathogenesis of pulmonary fibrosis in humans and murine models of lung fibrosis, however there is little direct experimental evidence that such viruses induce lung fibrosis in the natural host. The equine γHV EHV 5 is associated with equine multinodular pulmonary fibrosis (EMPF), a progressive fibrosing lung disease in its natural host, the horse. Experimental reproduction of EMPF has not been attempted to date. We hypothesized that inoculation of EHV 5 isolated from cases of EMPF into the lungs of clinically normal horses would induce lung fibrosis similar to EMPF. Neutralizing antibody titers were measured in the horses before and after inoculation with EHV 5. PCR and virus isolation was used to detect EHV 5 in antemortem blood and BAL samples, and in tissues collected postmortem. Nodular pulmonary fibrosis and induction of myofibroblasts occurred in EHV 5 inoculated horses. Mean lung collagen in EHV 5 inoculated horses (80 µg/mg) was significantly increased compared to control horses (26 µg/mg) (p < 0.5), as was interstitial collagen (32.6% ± 1.2% vs 23% ± 1.4%) (mean ± SEM; p < 0.001). Virus was difficult to detect in infected horses throughout the experiment, although EHV 5 antigen was detected in the lung by immunohistochemistry. We conclude that the γHV EHV 5 can induce lung fibrosis in the horse, and hypothesize that induction of fibrosis occurs while the virus is latent within the lung. This is the first example of a γHV inducing lung fibrosis in the natural host.

Histopathologic approach to the surgical lung biopsy in interstitial lung disease

Interpretation of lung biopsy specimens is an integral part in the diagnosis of interstitial lung disease (ILD). The process of evaluating a surgical lung biopsy for disease involves answering several questions. Unlike much of surgical pathology of neoplastic lung disease, arriving at the correct diagnosis in nonneoplastic lung disease often requires correlation with clinical and radiologic findings. The topic of ILD or diffuse infiltrative lung disease covers several hundred entities. This article is meant to be a launching point in the clinician's approach to the histologic evaluation of lung disease.

Pulmonary manifestations of rheumatoid arthritis

Pulmonary disease is a major source of morbidity and mortality in rheumatoid arthritis, manifesting most commonly as interstitial lung disease, airways disease, rheumatoid nodules, and pleural effusions. The diagnostic assessment of respiratory abnormalities is complicated by underlying risk for infection, the use of drugs with known pulmonary toxicity, and the frequency of lung disease related to rheumatoid arthritis itself. Evaluation and management of rheumatoid arthritis-associated pulmonary disease frequently necessitates a multidisciplinary approach.

A controlled trial of sildenafil in advanced idiopathic pulmonary fibrosis

BACKGROUND

Sildenafil, a phosphodiesterase-5 inhibitor, may preferentially improve blood flow to well-ventilated regions of the lung in patients with advanced idiopathic pulmonary fibrosis, which could result in improvements in gas exchange. We tested the hypothesis that treatment with sildenafil would improve walk distance, dyspnea, and quality of life in patients with advanced idiopathic pulmonary fibrosis, defined as a carbon monoxide diffusion capacity of less than 35% of the predicted value.

METHODS

We conducted a double-blind, randomized, placebo-controlled trial of sildenafil in two periods. The first period consisted of 12 weeks of a double-blind comparison between sildenafil and a placebo control. The primary outcome was the proportion of patients with an increase in the 6-minute walk distance of 20% or more. Key secondary outcomes included changes in oxygenation, degree of dyspnea, and quality of life. The second period was a 12-week open-label evaluation involving all patients receiving sildenafil.

RESULTS

A total of 180 patients were enrolled in the study. The difference in the primary outcome was not significant, with 9 of 89 patients (10%) in the sildenafil group and 6 of 91 (7%) in the placebo group having an improvement of 20% or more in the 6-minute walk distance (P=0.39). There were small but significant differences in arterial oxygenation, carbon monoxide diffusion capacity, degree of dyspnea, and quality of life favoring the sildenafil group. Serious adverse events were similar in the two study groups.

CONCLUSIONS

This study did not show a benefit for sildenafil for the primary outcome. The presence of some positive secondary outcomes creates clinical equipoise for further research. (Funded by the National Heart, Lung, and Blood Institute and others; ClinicalTrials.gov number, NCT00517933.)

[Acute exacerbation of idiopathic pulmonary fibrosis]

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive disease. Its natural history may have episodes of acute exacerbation (AE-IPF), whose best accepted definition would be a clinically significant acute worsening, without identified cause, in patients with an underlying IPF. The incidence of AE-IPF ranges from 5%-19% of patients per year. It is estimated that acute deterioration of the respiratory status occurred in 47% of these patients before death. A rapidly progressive dyspnoea is the most prominent symptom, with associated cough, fever and flu-like symptoms. The diagnosis is strengthened by the presence of leukocytosis on the blood count, neutrophilia on the bronchoalveolar lavage, and development of new diffuse bilateral ground-glass opacities superimposed on the pre-existing radiographic findings. The major histological finding is diffuse alveolar damage. Methylprednisolone seems to be the best therapeutic option, although the treatment response is usually poor.

Diffuse interstitial lung disease: overlaps and uncertainties

Histopathological analysis of lung biopsy material allows the diagnosis of idiopathic interstitial pneumonias; however, the strength of this diagnosis is sometimes subverted by interobserver variation and sampling. The American Thoracic Society and European Respiratory Society recommendations of 2002 provide a framework for the diagnosis of interstitial lung disease (ILD) and proposed an integrated clinical, radiological and histopathological approach. These recommendations represent a break with tradition by replacing the 'gold standard' of histopathology with the combined 'silver standards' of clinical, imaging and histopathological information. One of the pitfalls of a rigid classification system for the diagnosis of interstitial lung disease is its failure to accommodate the phenomenon of overlapping disease patterns. This article reviews the various ways that interstitial lung disease may be classified and discusses their applicability. In addition the issue of overlap disease patterns is considered in the context of histopathological interobserver variation and sampling error and how a pigeonhole approach to disease classification may overlook these hybrid entities.

[Histopathology of idiopathic diffuse interstitial lung diseases]

The diagnosis of interstitial disease requires a multidisciplinary approach and interaction between clinicians, radiologists, and pathologists. Pathologists must identify a model orpatternof histologic lesions that suggests a given interstitial disease, without prejudice to its idiopathic nature. Usual interstitial pneumonia (UIP), the designation used by pathologists for the clinical equivalent, idiopathic pulmonary fibrosis, is characterized histologically by fibrosis with a temporal and spatial heterogeneity, by the presence of fibroblastic foci, and by patches of subpleural and paraseptal honeycomb remodeling. Nonspecific interstitial pneumonia (NSIP) is the principal differential diagnosis for UIP, but contrary to UIP, has a good prognosis. The histologic appearance of NSIP is non-specific, and collagenoses, drug toxicity, immunologic lung diseases, and some infectious processes can present in this form. The diagnosis of NSIP is therefore a provisional diagnosis proposed by pathologists, while awaiting additional clinical and laboratory investigations to identify the cause; it is considered idiopathic only by default.

Heterogeneity in Combined Pulmonary Fibrosis and Emphysema

BACKGROUND

Combined pulmonary fibrosis and emphysema (CPFE) is a unique disorder described in several case series of upper lobe emphysema associated with lower lobe fibrosis. Patients with this entity have relatively preserved lung volumes and spirometry but marked reductions in diffusing capacity on pulmonary function testing. Smoking appears to be the predominant risk factor for this disorder. Usual interstitial pneumonia has been the most common histological pattern of interstitial lung disease described on biopsy in the literature.

OBJECTIVES

To characterize the clinical, imaging and pathological features of a cohort of patients with CPFE.

METHODS

Retrospective review of electronic medical record data, radiological imaging, and available lung biopsy specimens for a series of 10 patients with CPFE at the Providence VA Medical Center, Providence, R.I., USA.

RESULTS

We describe a series of 10 patients with CPFE. All had severe reductions in diffusing capacity out of proportion to their lung volumes and spirometry. All had predominantly upper lobe emphysema on computed tomography; 8/10 had lower lobe subpleural reticular abnormalities and honeycombing, while 2 had lower lobe ground glass changes on imaging. These 2 patients demonstrated a pattern of interstitial lung disease on biopsy characterized by intra-alveolar macrophage accumulation in association with marked alveolar septal fibrosis, consistent with a variant form of desquamative interstitial pneumonia with extensive fibrosis.

CONCLUSIONS

The imaging findings and pathology in patients with CPFE are heterogeneous.

Inflammation-associated remodelling and fibrosis in the lung - a process and an end point

Fibrosis by common usage in the pathological and clinical literature is the end result of a healing process and synonymous with scarring. We would argue that its use to describe a dynamic series of events which may be reversible is unhelpful and that the term 'lung remodelling' is a better description for this process as it reflects changes in tissue organization that may or may not progress to 'fibrosis' as a final fixed point. Resolution, through reversal of active lung remodelling, by therapeutic intervention is possible providing the alveolar architecture remains intact. If the lung architecture is lost then healing by permanent fibrosis with loss of organ function is inevitable.

Interstitial lung disease?the new synergy between radiology and pathology

In the last 30 years, high-resolution computed tomography (HRCT) has been the major advance in diagnosis of diffuse parenchymal lung disease (DPLD). We review the diagnostic accuracy of HRCT and discuss how the gold standard in diagnosis of DPLD has shifted from histopathological diagnosis in isolation to a multidisciplinary approach. This latter process is now accepted as providing the highest levels of diagnostic accuracy in patients with DPLD and lung biopsy is primarily reserved for cases with atypical clinical or radiological presentations.

National differences in reporting 'pneumonia' and 'pneumonia interstitial': an analysis of the WHO International Drug Monitoring Database on 15 drugs in nine countries for seven pulmonary conditions

PURPOSE

Increased post-marketing reports of 'interstitial pneumonia' as an adverse drug reaction (ADR) from the use of gefitinib, irinotecan, or leflunomide among patients in Japan have not been noted in other countries. The WHO International Drug Monitoring Database was analyzed to examine Japan's pattern of reporting the term 'pneumonia interstitial' for 15 selected drugs with a mixed history of association with pulmonary ADRs.

METHODS

ADR counts from the WHO Database for 1992-2001 were obtained for 15 disparate drugs (three androgen blockers, eight cytotoxics, one proton pump inhibitor, one monoclonal antibody, and two anti-epileptics) from nine countries (Australia, France, Germany, Italy, Japan, Spain, Thailand, U.K., and U.S.A.) for seven pulmonary ADR terms (alveolitis fibrosing, pneumonia, pulmonary fibrosis, lung fibrosis interstitial, pulmonary infiltration, interstitial lung disease, and pneumonia interstitial). Statistical analyses included estimating Poisson-distributed expected rates, observed/expected (O/E) ratios, and 95% confidence intervals (CI). The overlapping nature and changes in definition over time of these terms in medical texts and in the WHO-ART, COSTART, J-ART, and MedDRA coding systems is also noted.

RESULTS

Compared to other countries, both Japan and France did not have higher O/E reporting ratios for all seven pulmonary ADRs combined, but did have higher O/E ratios for 'pneumonia interstitial' and lower O/E ratios for 'pneumonia' for the same drugs.

CONCLUSIONS

Japan and France were found to preferentially use the term 'pneumonia interstitial' for ADR where other countries used 'pneumonia.' This cultural pattern coincides with the fact that 'pneumonia interstitial' in older versions of COSTART, J-ART, and MedDRA were subsumed under infectious pulmonary diseases.

Current concepts in the classification of interstitial lung disease

The diagnosis and classification of idiopathic interstitial pneumonias continue to be problematic areas for pathologists. The recently proposed American Thoracic Society/European Respiratory Society International Multidisciplinary Consensus Classification of the Idiopathic Interstitial Pneumonias defines specific clinical, radiologic, and pathologic criteria for each of the pulmonary disorders that encompass the idiopathic interstitial pneumonias. In this review, the highlights of this classification are presented, along with recommended guidelines for handling lung biopsy specimens and diagnosing interstitial lung diseases.

Role of Thoracic Surgeons in the Diagnosis of Idiopathic Interstitial Lung Disease

The interstitial lung disorders are a heterogenous group of pulmonary disorders in which the interstitium is the predominant tissue type involved in the disease process. The idiopathic interstitial pneumonias represent a subgroup of these disorders that can be distinguished by unique clinical, radiologic, and pathologic features. Recent changes have been made in the classification system, with important distinctions between idiopathic pulmonary fibrosis and the other idiopathic interstitial pneumonias. Surgical lung biopsy remains the gold standard for diagnosis. However, controversy exists regarding the methods and indications for biopsy. In this article, we review the salient clinical, radiologic, and pathologic features of these unique disorders as well as the updated classification scheme. We also discuss the current methods, approaches, and indications for biopsy.

Nonspecific interstitial pneumonia: a real clinical entity?

Based on the current multidisciplinary classification of idiopathic interstitial pneumonia (IIP) organized by ATS/ERS, nonspecific interstitial pneumonia (NSIP) is considered as one type of IIP. An incidence of idiopathic NSIP is relatively small and possesses clinical features that are different than idiopathic pulmonary fibrosis (IPF) and usual interstitial pneumonia (UIP). Because there is little evidence of a long-term prognosis in patients with NSIP, some of them have an unfavorable prognosis similar to IPF/UIP. We review the significance of prognostic factors that have been reported in patients with IPF/UIP by applying them to patients with NSIP. The association with collagen vascular diseases focuses on etiologic background. Finally, the article discusses whether NSIP could be an early lesion of UIP based on the reported evidence and our own professional experiences.

Desquamative interstitial pneumonia, respiratory bronchiolitis and their relationship to smoking

AIMS

Respiratory bronchiolitis (RB) and desquamative interstitial pneumonia (DIP) are closely associated histological patterns of interstitial pneumonia, although there are no studies on the extent of individual histological parameters. Furthermore, the term smoking related-interstitial lung disease (SR-ILD) has been proposed as a term to encompass patients with both these histological patterns who give a history of smoking, though it is not well defined how this term relates to historical cases of DIP. The aim of this study was to compare histological parameters in cases of DIP and RB and then to review in detail clinical, imaging and histological data for DIP in relation to a history of smoking.

METHODS AND RESULTS

Forty-nine cases were reviewed, 24 with RB and 25 with DIP; five cases of DIP were re-classified as RB on review due to bronchocentricity of the infiltrate. There was a significantly greater extent of interstitial fibrosis (P = 0.02), lymphoid follicles (P < 0.001) and eosinophilic infiltration (P < 0.0001) in patients with DIP compared with RB. In addition, the extents of these three parameters were significantly interrelated. Patients with DIP had a lower incidence of smoking (60%) when compared with patients with RB-ILD (93%) (P < 0.005). Further analysis of smokers versus never-smokers with DIP showed no difference in histological parameters, extent of haemosiderin deposition or the number of CD1a+ macrophages between the two groups, nor were there any differences in clinical data to suggest other aetiologies. Follow-up high-resolution computed tomography data from patients with DIP suggested that a pattern of fibrotic non-specific interstitial pneumonia (NSIP) may develop in the long term in both smokers and never-smokers.

CONCLUSION

There are significant differences in the extent of interstitial fibrosis, lymphoid follicles and eosinophilic infiltration between DIP and RB, as well as a much lower incidence of smoking in patients with DIP. Whether the lower reported incidence of smoking in DIP reflects referral bias or conservatism in giving a history of smoking remains uncertain, as neither histological parameters nor clinical data indicate a difference between smokers and never-smokers with DIP. Nevertheless, some cases of DIP are likely to remain idiopathic and unrelated to RB, though still have a good prognosis. Furthermore, they may evolve into a pattern resembling fibrotic NSIP. Therefore, whilst SR-ILD is appropriate in the correct clinical setting, the distinction between the histological patterns of RB and DIP remains appropriate.

[DIP (desquamative interstitial pneumonia): as a tobacco-associated disease -- case report]

DIP (desquamative interstitial pneumonia) is an interstitial lung disease with diffuse and uniform accumulation of alveolar macrophages. There is a strong association with tobacco since 90% of the patients are smokers. The interstitial lung diseases related to tobacco are diverse and include tumours, emphysema, chronic bronchitis, RBILD (Respiratory Bronchilites associated Interstitial Lung Disease), DIP and Langerhans Cell Histiocitosis. The authors present a case of DIP. A brief theorycal revision and discussion of a case is made facing the association with tobacco.

[Cryptogenic organizing pneumonia -- case report]

Cryptogenic organizing pneumonia (COP) is one of the new recognized histological patterns of idiopathic interstitial pneumonias, in witch no cause or association is identified. Idiopathic bronchiolitis obliterans-organizing pneumonia (BOOP) is a synonymous. This rare entity is characterized by involvement of alveoli and bronchioles, which are filled by intraluminal polyps of fibroblastic tissue (Masson bodies). The clinical presentation often mimics that of community-acquired pneumonia. Persistent non-productive cough, dyspnoea with exertion and weight loss are common features, and in one-half of the cases the onset is heralded by a flu-like syndrome. Definitive diagnosis depends on histological data, and video-assisted thoracoscopic (VAT) has become the established technique. Spontaneous recovery is rare; corticosteroid therapy provides cure in two thirds of cases. The authors present a case of a patient whose lung biopsy by VAT confirmed the diagnosis. She was treated with corticoids without recurrence in a two year follow-up.

Identification of Spontaneous Feline Idiopathic Pulmonary Fibrosis

STUDY OBJECTIVES

Idiopathic pulmonary fibrosis (IPF) is a poorly understood chronic respiratory disease of humans, which has no correlate in other animals. Understanding the role that inflammation, alveolar epithelial cells, and myofibroblasts play in the progression of the disease is controversial, and hampered by the lack of an animal model. We have identified spontaneous IPF in domestic cats and hypothesized that this newly identified disease shares the pathology of human IPF; further, this work provides data suggesting that the disease is related to a defect in type II pneumocyte biology.

SETTING AND SUBJECTS

Chronic respiratory disease with pathology consistent with usual interstitial pneumonia (UIP) spontaneously developed in 16 domestic cats.

RESULTS

The histopathology of feline IPF consisted of the following: (1) interstitial fibrosis with fibroblast/myofibroblast foci, (2) honeycombing with alveolar epithelial metaplasia and type II pneumocyte hyperplasia, and (3) alveolar interstitial smooth-muscle metaplasia. Interstitial inflammation was not a prominent feature of the disease. alpha-Smooth muscle actin-positive myofibroblasts were prominent in myofibroblast foci, beneath honeycomb and hyperplastic epithelium, and in alveolar septa away from the remodeling. Feline IPF type II pneumocyte ultrastructure is similar to a heritable form of human IPF, with abnormal cytoplasmic lamellar body-like inclusions.

CONCLUSIONS

We conclude the following: (1) chronic respiratory disease with clinical and pathology features of UIP/IPF occurs in the domestic cat; (2) as in human IPF, the type II pneumocyte and myofibroblasts are important cellular constituents of feline IPF; and (3) type II cell ultrastructure suggests feline IPF is a defect in the type II pneumocyte.

Augmented pulmonary IL-4 and IL-13 receptor subunit expression in idiopathic interstitial pneumonia

BACKGROUND

Some idiopathic interstitial pneumonias (IIPs) are characterised by fibroproliferation and deposition of extracellular matrix. Because efficacious treatment options are limited, research has been directed towards understanding the cytokine networks that may affect fibroblast activation and, hence, the progression of certain IIPs.

AIMS

To examine the expression of interleukin 4 (IL-4), IL-13, and their corresponding receptor subunits in the various forms of IIP and normal patient groups.

METHODS

Molecular and immunohistochemical analysis of IL-4, interferon gamma (IFNgamma), IL-13, IL-4 receptor (IL-R), and IL-13 receptor subunits in surgical lung biopsies (SLBs) from 39 patients (21 usual interstitial pneumonia (UIP), six non-specific interstitial pneumonia (NSIP), eight respiratory bronchiolitic interstitial lung disease (RBILD), and five normal controls).

RESULTS

Molecular analysis demonstrated that IL-13Ralpha2, IL-13Ralpha1, and IL-4Ralpha were present in a greater proportion of upper and lower lobe biopsies from patients with UIP than patients with NSIP and RBILD. Immunohistochemical analysis of patients with UIP, NSIP, and RBILD revealed interstitial staining for all three receptor subunits, whereas such staining was only seen in mononuclear cells present in normal SLBs. Fibroblastic foci in patients with UIP strongly stained for IL-4Ralpha and IL-13Ralpha2. Localised expression of IL-4Ralpha was also seen in SLBs from patients with NSIP but not in other groups.

CONCLUSION

Some histological subtypes of IIP are associated with increased pulmonary expression of receptor subunits responsive to IL-4 and IL-13. These findings may be of particular importance in understanding the pathogenesis of IIP and, more importantly, may provide important novel therapeutic targets.

A 5-week-old HIV-1–exposed girl with failure to thrive and diffuse nodular pulmonary infiltrates

A 5-week-old female infant with vertical HIV-1 exposure, progressive cough, and failure to thrive was given a diagnosis of bilateral diffuse nodular lung lesions. The child was without fever, leukocytosis, anemia, peripheral adenopathy, or hepatosplenomegaly, and the results of repeated blood tests for HIV-1 DNA were negative. A needle biopsy of the lungs revealed granulomatous inflammation and giant cells, with fungal organisms suggestive of Aspergillus species. A nitroblue tetrazolium dye test performed on the patient's blood specimen demonstrated absence of dye reduction, suggesting a diagnosis of chronic granulomatous disease. Further analysis revealed that the child had a deficiency of the p47(phox) component of the nicotinamide adenine dinucleotide phosphate oxidase system. Thus this child with vertical HIV-1 exposure and diffuse pulmonary nodules actually had an autosomal recessive form of chronic granulomatous disease. This case study clearly demonstrates that children with suspected HIV-1 infection might also need evaluation for primary immunodeficiency and that the clinical immunology laboratory is a powerful adjunct in coming to a correct diagnosis.

Recent advances in the diagnosis and management of nonspecific interstitial pneumonia

Idiopathic interstitial pneumonia is a heterogeneous group of diseases. Recently, the importance of a detailed differentiation of nonspecific interstitial pneumonia from other idiopathic interstitial pneumonias has been demonstrated. Most critical appeared to be a proper classification based on clinical presentation, high-resolution CT findings, bronchoalveolar lavage fluid cell findings, and histopathology. This classification may guide the most appropriate therapeutic approach and has significant implications regarding prognosis. Recent advances in the diagnosis and management of nonspecific interstitial pneumonia, cellular and fibrosing variants, are discussed.