Eosinophilic pneumonia-like areas in idiopathic usual interstitial pneumonia

Idiopathic Chronic Eosinophilic Pneumonia Evolving to Pulmonary Fibrosis: A Retrospective Analysis

BACKGROUND

Patients with idiopathic chronic eosinophilic pneumonia (ICEP) may have pulmonary fibrosis.

OBJECTIVES

To investigate the predictors of pulmonary fibrosis in ICEP, to describe the timeline of pulmonary fibrosis after ICEP diagnosis, and to detail the radiologic pattern of fibrosis.

METHODS

A retrospective computer-assisted search was performed to identify patients with ICEP seen at Mayo Clinic in Rochester, Minnesota, from January 1, 1997, through September 1, 2019. Patients with follow-up chest computed tomography (CT) beyond 12 months after the ICEP diagnosis were included in the study. Demographic, clinical, radiologic, and histopathologic characteristics were analyzed. Proportional hazards regression was used to assess the predictors of pulmonary fibrosis.

RESULTS

We identified 62 patients (mean [SD] age at ICEP diagnosis, 60 [13] years; female sex, 37 [60%]). Cough (87%) and shortness of breath (85%) were the most common presenting symptoms. Of patients, 27 (44%) had a history of smoking and 27 (44%) had a history of asthma. During follow-up, 23 patients (37%) had CT evidence of pulmonary fibrosis, of whom 16 patients (70%) had a CT pattern inconsistent with usual interstitial pneumonia. In 29% of the patients, the CT evidence of pulmonary fibrosis developed within 2 years after ICEP. Age and male sex were predictors of pulmonary fibrosis. Of note, a history of asthma decreased the likelihood of pulmonary fibrosis.

CONCLUSIONS

Development of pulmonary fibro-sis is not uncommon in patients with ICEP, especially older men, and is associated with increased risk of death.

Immunophenotyping of Acute Inflammatory Exacerbations of Lung Injury Driven by Mutant Surfactant Protein-C: A Role for Inflammatory Eosinophils

Acute inflammatory exacerbations (AIEs) represent immune-driven deteriorations of many chronic lung conditions, including COPD, asthma, and pulmonary fibrosis (PF). The first line of therapy is represented by broad-spectrum immunomodulation. Among the several inflammatory populations mobilizing during AIEs, eosinophils have been identified as promising indicators of an active inflammatory exacerbation. To better study the eosinophil-parenchymal crosstalk during AIE-PF, this work leverages a clinically relevant model of inflammatory exacerbations triggered by inducible expression of a mutation in the alveolar epithelial type 2 cell Surfactant Protein-C gene [SP-C^I73T]. Unbiased single-cell sequencing analysis of controls and SP-C^I73T mutants at a time coordinated with peak eosinophilia (14 days) defined heightened inflammatory activation, chemotaxis, and survival signaling (IL-6, IL-4/13, STAT3, Glucocorticoid Receptor, mTOR, and MYC) in eosinophils. To study the impact of eosinophils in inflammatory exacerbations, the SP-C^I73T line was crossed with eosinophil lineage deficient mice (GATA1^Δdbl) to produce the SP-C^I73TGATA1^KO line. Time course analysis (7-42 days) demonstrated improved lung histology, survival, and reduced inflammation in SP-C^I73TGATA1^KO cohorts. Spectral flow cytometry of tissue digests confirmed eosinophil depletion in GATA1^KO mice and the absence of a compensatory shift in neutrophils and immature monocyte recruitment. Eosinophil deletion resulted in progressive monocyte-derived macrophage accumulation (14 days post-injury), combined with declines in CD3⁺CD4⁺ lymphocyte and B220⁺ B cell abundance. Histochemical analysis revealed atypical inflammatory cell activation in SP-C^I73TGATA1^KO mice, with reduced numbers of Arg-1⁺ and iNOS⁺ cells, but increases in tgfb1 mRNA expression in bronchoalveolar lavage cells and tissue. Dexamethasone treatment (1 mg/kg daily, i.p.) was utilized to investigate corticosteroid efficacy in highly eosinophilic exacerbations induced by mutant SP-C^I73T. Dexamethasone successfully reduced total and eosinophil (CD11b⁺SigF⁺CD11c^-) counts at 14 days and was linked to reduced evidence of structural damage and perivascular infiltrate. Together, these results illustrate the deleterious role of eosinophils in inflammatory events preceding lung fibrosis and demonstrate the efficacy of corticosteroid treatment in highly eosinophilic exacerbations induced by mutant SP-C^I73T.

Eosinophil alveolitis in two patients with idiopathic pulmonary fibrosis

Bronchoalveolar lavage fluid (BALF) in patients with idiopathic pulmonary fibrosis (IPF) is typically characterized by a neutrophil inflammatory pattern and to a lesser extent (<25%) a mild eosinophil alveolitis. We here present two patients with a definite usual interstitial pneumonia (UIP) pattern on high-resolution computed tomography of the thorax (HRCT) which demonstrated unusually high eosinophil counts in the BALF (40% and 51%). Based on HRCT, lack of response to steroids and the disease course they were both diagnosed as IPF after a multidisciplinary team discussion. This report discusses the diagnostic and etiological considerations of a coexisting UIP pattern and an eosinophil alveolitis. We conclude that these cases illustrate that high level BALF eosinophilia (40–50%) may occur among patients with IPF.

Eosinophilic pneumonias in children: A review of the epidemiology, diagnosis, and treatment

Pediatric eosinophilic pneumonias (EPs) are characterized by a significant infiltration of the alveolar spaces and lung interstitium by eosinophils, with conservation of the lung structure. In developed countries, EPs constitute exceptional entities in pediatric care. Clinical symptoms may be transient (Löffler syndrome), acute (<1 month and mostly <7 days), or chronic (>1 month). Diagnosis relies on demonstration of alveolar eosinophilia on bronchoalveolar lavage, whether or not associated with blood eosinophilia. EPs are a heterogeneous group of disorders divided into: (i) secondary forms (seen mainly in parasitic infections, allergic bronchopulmonary aspergillosis, and drug reactions); and (ii) primary forms (eosinophilic granulomatosis with polyangiitis, hypereosinophilic syndrome, idiopathic chronic eosinophilic pneumonia, and idiopathic acute eosinophilic pneumonia). Despite their rarity, the etiological approach to EP must be well-defined as some causes can be rapidly life-threatening without initiation of the proper treatment. This approach (i) eliminates secondary forms, with comprehensive history taking and minimal biological assessment, (ii) is oriented in primary forms by the acute or chronic setting, and the existence of extrapulmonary symptoms. Treatment of primary forms has traditionally relied on corticosteroids, usually with a dramatic response. Specific treatments or the adjunction of corticosteroid-sparing treatment or immunosuppressors are currently being evaluated in order to improve the prognosis and the side effects associated with corticosteroid treatment in a pediatric setting.

The role of histology in idiopathic pulmonary fibrosis: an update

The diagnosis of idiopathic pulmonary fibrosis (IPF) currently requires an integrated clinical-radiological-pathological approach in which the histology plays a different role from in the past. The first reason for this change is that non-invasive diagnostic procedures, particularly pulmonary function tests and high resolution computed tomography, have become increasingly competitive with biopsy in providing prognostic information. The other reason is a better appreciation of the limitations of histology: sampling error and interobserver variation. In this review we analyze the reasons for this change of perspective, provide an update on the practical role of histology in the diagnosis of IPF and discuss some of its complications.

Eosinophilic pneumonias

Eosinophilic pneumonias (EP) encompass a wide spectrum of lung diseases characterized by peripheral blood eosinophilia (>1 x 10(9) eosinophils/l) and/or alveolar eosinophilia (>25%). Blood eosinophilia may be lacking, as in the early phase of idiopathic acute EP, or in patients already taking oral corticosteroids. EP may present with varying severity, ranging from almost asymptomatic infiltrates to the acute respiratory distress syndrome necessitating mechanical ventilation. Possible causes of EP must be thoroughly investigated, especially drugs and the variety of parasitic infections (considering history of travel or residence in areas of endemic parasitic infection). However, chronic EP remains idiopathic in many cases. When present, extrathoracic manifestations lead to suspect Churg-Strauss syndrome (CSS) or the hypereosinophilic syndrome (HES), the prognosis of which is dominated by cardiac involvement. Apart from the treatment of specific causes when possible, corticosteroids remain the cornerstone of symptomatic treatment for eosinophilic disorders, usually with a dramatic response, but frequent relapses when tapering or after stopping the treatment. The adjunction of immunosuppressants to corticosteroids is necessary in patients with CSS and poor prognosis factors. Imatinib has recently proven effective in the treatment of the myeloproliferative variant of the HES.

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

Since Liebow and Carrington's original classification of idiopathic interstitial pneumonias, there have been controversies over which histological patterns should be included and how they relate to clinicopathological diseases such as cryptogenic fibrosing alveolitis/idiopathic pulmonary fibrosis (CFA/IPF). Because of these differences and the wealth of overlapping terminology, a consensus classification system has been proposed, devised by a group of clinicians, radiologists and pathologists. Seven histological patterns are recognized: usual interstitial pneumonia (UIP), non-specific interstitial pneumonia (NSIP), diffuse alveolar damage (DAD), organizing pneumonia (OP), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis (RB) and lymphocytic interstitial pneumonia (LIP), each with a clinicopathological counterpart, the most well defined being UIP and CFA/IPF. The system is applicable both in terms of the pathologist identifying histological patterns in isolation and in terms of the pathologist's role in contributing to the final clinicopathological diagnosis. It will probably provide greater consistency in diagnosis, early studies suggesting that the system is reproducible, and also identify purer cohorts for studies investigating causation. It also highlights the fact that the 'gold standard for diagnosis' is no longer a surgical lung biopsy in isolation but more the clinicopathological conference, when clinical, imaging and histological data are jointly discussed to produce the final clinicopathological diagnosis.