Histologic findings in lung biopsies in patients with suspected graft-versus-host disease

The Pathology of Pulmonary Disease After Pediatric Hematopoietic Stem Cell Transplantation

Pulmonary complications continue to cause significant morbidity and mortality in posthematopoietic stem cell transplantation (HSCT) settings. The histopathology of pulmonary diseases in the post-HSCT context is poorly characterized, especially in the pediatric population. We sought to characterize the pathologic spectrum of pulmonary disease post-HSCT in a pediatric cohort. Fifty-six specimens, including 53 biopsy specimens, corresponding to 53 patients, were identified. Biopsy slides were reviewed and assigned to diagnostic categories (infectious, graft-versus-host disease, vasculopathy, indeterminate, and others) by consensus among 3 pediatric pulmonary pathologists, taking into consideration pathologic, clinical, radiologic, and laboratory findings. The most common diagnostic category was infection (n=20). Vasculopathy, mostly in the form of fibromyxoid intimal expansion, was very common in the entire cohort (n=26) and was the sole finding in a small subset of patients (n=5), with particularly poor outcomes. A subset of biopsies remained indeterminate (n=10), and the findings in this cohort were dominated by acute lung injury. The latter group had a poor prognosis, with a short biopsy-to-death interval. The overall clinicopathologic concordance was 40%, most commonly agreeing in the infectious category. Finally, wedge biopsies led to a change in management in 69% of cases versus 23% of limited procedures (i.e., core needle biopsies). Our results suggest that while infectious complications continue to be common post-HSCT, other findings such as vasculopathy and acute lung injury portend a particularly poor prognosis and should be actively sought and reported.

Pulmonary Histopathologic Findings in Pediatric Patients After Hematopoietic Stem Cell Transplantation: An Autopsy Study

BACKGROUND

Pathologic characterization of pulmonary complications following hematopoietic stem cell transplantation (HSCT) is limited. We describe lung findings in pediatric patients who died following HSCT and attempt to identify potential clinical associations.

METHODS

Pathology databases at Texas Children's Hospital and the Children's Hospital of Philadelphia were queried (2013-2018 CHOP and 2017-2018 TCH). Electronic medical records and slides were reviewed.

RESULTS

Among 29 patients, 19 received HSCT for hematologic malignancy, 8 for non-malignant hematologic disorders, and 2 for metastatic solid tumors. Twenty-five patients (86%) showed 1 or more patterns of acute and organizing lung injury. Sixty-two percent had microvascular sclerosis, with venous involvement noted in most cases and not correlating with clinical history of pulmonary hypertension, clinical transplant-associated thrombotic microangiopathy, irradiation, or graft-versus-host disease. Features suggestive of graft-versus-host-disease were uncommon: 6 patients had lymphocytic bronchiolitis, and only 2 patients had evidence of bronchiolitis obliterans (both clinically unexpected), both with a mismatched unrelated donor transplant.

CONCLUSIONS

Acute and subacute alveolar injury (diffuse alveolar damage or organizing pneumonia) is common in pediatric patients who died following HSCT and is difficult to assign to a specific etiology. Microvascular sclerosis was frequent and did not correlate with a single distinct clinical feature.

Dual inhibition of the MEK/ERK and PI3K/AKT pathways prevents pulmonary GVHD suppressing perivenulitis and bronchiolitis

Patients with pulmonary graft-versus-host disease (pGVHD) have a poor prognosis after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Furthermore, pGVHD pathogenesis is not fully elucidated in humans, and currently available immunosuppressants are inadequately effective. We performed pathologic evaluation of lung specimens from 45 allo-HSCT recipients with pGVHD who underwent lung transplantation. Patient pathology was characterized by bronchiolitis and subpleural perivascular inflammation, with B-cell, monocyte, and T-cell accumulation around bronchioles. Bronchiolitis, perivascular inflammation, and peribronchial macrophage aggregation were also identified in a murine pGVHD model after transplant of bone marrow cells and splenocytes from C57BL/6 to B10.BR mice. Among mitogen-activated protein kinase kinase (MEK) inhibitors, cobimetinib, but not trametinib, improved survival rates. Cobimetinib attenuated bronchiolitis, improved airway resistance and lung compliance in the mice, and suppressed activation of B cells and tumor necrosis factor α production by monocytes in vitro; these features were not suppressed by trametinib or tacrolimus. Furthermore, cobimetinib suppressed activation of phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling, resulting in B-cell and monocyte suppression. Dual inhibition of the MEK/extracellular signal-regulated kinase (ERK) and PI3K/AKT pathways using a combination of trametinib and the PI3K inhibitor taselisib strongly suppressed B-cell activation in vitro and improved mouse survival rates compared with vehicle or monotherapy with trametinib or taselisib. Imaging mass cytometry of human pGVHD revealed that T cells around bronchioles were positive for phosphorylated ERK, whereas B cells were positive for phosphorylated AKT. Thus, perivascular inflammation and bronchiolitis mediated by activation of the MEK/ERK and PI3K/AKT pathways are essential for pGVHD and represent a potential novel therapeutic target in humans.

Cyclosporin A: A Repurposable Drug in the Treatment of COVID-19?

Coronavirus disease 2019 (COVID-19) is now at the forefront of major health challenge faced globally, creating an urgent need for safe and efficient therapeutic strategies. Given the high attrition rates, high costs, and quite slow development of drug discovery, repurposing of known FDA-approved molecules is increasingly becoming an attractive issue in order to quickly find molecules capable of preventing and/or curing COVID-19 patients. Cyclosporin A (CsA), a common anti-rejection drug widely used in transplantation, has recently been shown to exhibit substantial anti-SARS-CoV-2 antiviral activity and anti-COVID-19 effect. Here, we review the molecular mechanisms of action of CsA in order to highlight why this molecule seems to be an interesting candidate for the therapeutic management of COVID-19 patients. We conclude that CsA could have at least three major targets in COVID-19 patients: (i) an anti-inflammatory effect reducing the production of proinflammatory cytokines, (ii) an antiviral effect preventing the formation of the viral RNA synthesis complex, and (iii) an effect on tissue damage and thrombosis by acting against the deleterious action of angiotensin II. Several preliminary CsA clinical trials performed on COVID-19 patients report lower incidence of death and suggest that this strategy should be investigated further in order to assess in which context the benefit/risk ratio of repurposing CsA as first-line therapy in COVID-19 is the most favorable.

Non-classical manifestations of acute GVHD

Acute graft-versus-host disease (GVHD) is a major life-threatening complication after allogeneic hematopoietic cell transplantation (allo-HCT). The classical target organs of acute GVHD include the intestines, liver, and skin. The damage of these organs is relatively easy to detect for the clinician as diarrhea, increased bilirubin, and rash. However, there is increasing evidence that also other organs, where the acute damage is less apparent or more difficult to distinguish from drug toxicity, such as the central nervous system, the lungs, the ovaries and testis, the thymus, the bone marrow and the kidney, can be target organs of acute GVHD. Here, we review current evidence for non-classical manifestations of acute GVHD in rodent models and in patients and discuss them in the context of novel emerging therapies for GVHD. A better understanding of the involvement of the non-classical GVHD target organs may help to improve patient outcomes after allo-HCT.

Acute Pulmonary Graft-Versus-Host Disease in a Patient with Adult T-cell Leukemia-Lymphoma Diagnosed by a Cryobiopsy

A 51-year-old woman with adult T-cell leukemia-lymphoma was hospitalized in order to undergo allogeneic hematopoietic stem-cell transplantation. On day 29 after transplantation, she began to experience hypoxia upon exertion. Chest computed tomography revealed centrilobular granular shadows, and pulmonary function tests revealed a remarkable obstructive ventilatory impairment compared to before transplantation. A histopathological analysis following a transbronchial lung cryobiopsy revealed acute graft-versus-host disease (GVHD). We herein report a rare case of histopathologically diagnosed acute pulmonary GVHD with spontaneous remission.

Mimickers of pulmonary lymphoma

There are multiple entities that involve the lung that have radiographic, clinical, and morphologic overlaps with pulmonary lymphoma. In this review, we will discuss these entities in detail and provide relevant updates.

Perspectives in veterinary medicine: Description and classification of bronchiolar disorders in cats

This Perspectives in Veterinary Medicine article seeks to define, describe putative causes, and discuss key diagnostic tests for primary and secondary bronchiolar disorders to propose a classification scheme in cats with support from a literature review and case examples. The small airways (bronchioles with inner diameters <2 mm), located at the transitional zone between larger conducting airways and the pulmonary acinus, have been overlooked as major contributors to clinical syndromes of respiratory disease in cats. Because the trigger for many bronchiolar disorders is environmental and humans live in a shared environment with similar susceptibility, understanding these diseases in pet cats has relevance to One Health. Thoracic radiography, the major imaging modality used in the diagnostic evaluation of respiratory disease in cats, has low utility in detection of bronchiolar disease. Computed tomography (CT) with paired inspiratory and expiratory scans can detect pathology centered on small airways. In humans, treatment of bronchiolar disorders is not well established because of heterogeneous presentations and often late definitive diagnosis. A review of the human and veterinary medical literature will serve as the basis for a proposed classification scheme in cats. A case series of cats with CT or histopathologic evidence of bronchiolar lesions or both, either as a primary disorder or secondary to extension from large airway disease or interstitial lung disease, will be presented. Future multi‐institutional and multidisciplinary discussions among clinicians, radiologists, and pathologists will help refine and develop this classification scheme to promote early and specific recognition and optimize treatment.

Lung histopathology of non-infectious pulmonary complications after allogeneic haematopoietic stem cell transplantation

AIMS

Non-infectious pulmonary complications (NIPCs) occur frequently following allogeneic haematopoietic stem cell transplantation (HSCT). As there is no consensus on the description of the related pulmonary pathological lesions, pathologist reports and clinical conclusions are largely inconsistent in routine practice. The aim of our study was to provide an accurate overview of post-allogeneic HSCT NIPCs from a large number of lung biopsies.

METHODS AND RESULTS

We reviewed 61 lung biopsies in patients with an NIPC, including 51 surgical lung biopsies, four post-mortem biopsies and six lung explants. We found both bronchiolar (n = 59) and alveolar/interstitial pathologies (n = 27). We describe two types of bronchiolar lesions: bronchiolectasies (n = 37) and fibrous and cellular lesions with luminal narrowing (n = 43). We found a wide spectrum of airway/interstitial pathologies that were labelled using the terminology of the 2013 American Thoracic Society and European Respiratory Society (ATS/ERS) classification of idiopathic interstitial pneumonias (IIPs), including the following: organising pneumonia (OP, n = 8), non-specific interstitial pneumonia (NSIP, n = 9), diffuse alveolar damage (DAD, n = 6), lymphoid interstitial pneumonia (LIP, n = 1) and pleuroparenchymal fibroelastosis (PPFE, n = 2), as well as one instance of associated PPFE and NSIP.

CONCLUSIONS

Interstitial pathology was associated with bronchiolar lesions in 41% of the cases reviewed (n = 25). Lung airway and interstitial inflammation was still present in lung explants from patients who underwent lung transplantation for post-allogeneic HSCT end-stage respiratory insufficiency. Herein, we describe a wide spectrum of pathological lung lesions encountered in post-allogeneic HSCT NIPCs.

Inhibition of 5-lipoxygenase alleviates graft-versus-host disease

Rezende et al. report that the transplant of 5-lipoxygenase (5-LO)−deficient leukocytes protects mice from GVHD. Treatment with the 5-LO inhibitor zileuton or a LTB₄ antagonist at the initial phase of the transplant achieves similar protective effects. 5-LO is a crucial contributor to tissue damage in GVHD.

Leukotriene B₄ (LTB₄), a proinflammatory mediator produced by the enzyme 5-lipoxygenase (5-LO), is associated with the development of many inflammatory diseases. In this study, we evaluated the participation of the 5-LO/LTB₄ axis in graft-versus-host disease (GVHD) pathogenesis by transplanting 5-LO–deficient leukocytes and investigated the effect of pharmacologic 5-LO inhibition by zileuton and LTB₄ inhibition by CP-105,696. Mice that received allogeneic transplant showed an increase in nuclear 5-LO expression in splenocytes, indicating enzyme activation after GVHD. Mice receiving 5-LO–deficient cell transplant or zileuton treatment had prolonged survival, reduced GVHD clinical scores, reduced intestinal and liver injury, and decreased levels of serum and hepatic LTB₄. These results were associated with inhibition of leukocyte recruitment and decreased production of cytokines and chemokines. Treatment with CP-105,696 achieved similar effects. The chimerism or the beneficial graft-versus-leukemia response remained unaffected. Our data provide evidence that the 5-LO/LTB₄ axis orchestrates GVHD development and suggest it could be a target for the development of novel therapeutic strategies for GVHD treatment.

Pneumocyte injury and ubiquitin-positive pneumocytes in interstitial lung diseases

Pneumocyte injury is a characteristic of pulmonary interstitial pneumonias (IPs). Histological markers of pneumocyte injury and inflammation include pneumocyte necrosis, erosion, hyaline membrane and fibrin exudation with subsequent intraluminal granulation tissue formation. We found that intracytoplasmic inclusions in pneumocytes are ubiquitin-positive (Ub⁺) and that the number of Ub⁺ pneumocytes shows positive correlation with the extent of diffuse alveolar damage (DAD). To determine the role of Ub⁺ pneumocytes and inclusions in IPs, we studied their relationship with pathological and clinical features of DAD, usual interstitial pneumonia (UIP) and organizing pneumonia (OP), including airspace enlargement with fibrosis (AEF). We analysed Ub⁺ pneumocytes, inclusions, erosions and intraluminal granulation tissue in relation to pneumocyte injury. The numbers of immunohistochemically identified Ub⁺ inclusions in each IP were higher than the number of inclusions detected by light microscopy. The inclusions detected by Ub⁺ immunostaining were identical to the inclusions observed by light microscopy. UIP and DAD had many Ub⁺ inclusions, while OP and AEF had fewer Ub⁺ inclusions. These results suggest that the extent of Ub⁺ inclusions reflects the severity of pneumocyte injury among IPs. Thus, Ub⁺ inclusions are a histological marker of pneumocyte injury that may be helpful in determining the severity and prognosis of IPs.

Hematopoietic stem cell transplantation: graft versus host disease and pathology of gastrointestinal tract, liver, and lung

Hematopoietic stem cell transplantation (HCT), formerly known as bone marrow transplantation, is an integral part of treatment for many hematological malignancies. HCT is associated with several complications and comorbidities with differential effects on a wide spectrum of organs and tissues. We present an update on HCT-associated complications such as graft versus host disease (GVHD) and infection, with focus on the surgical pathology of the gastrointestinal (GI) tract, liver, and lung. Although the grading system for GI tract acute GVHD was proposed 40 years ago, recent studies have shed light on minimal histologic criteria for diagnosis of GVHD, as well as its differential diagnosis, including histologic effects of various medications. GI dysfunction in autologous transplant recipients is increasingly appreciated and patients are often biopsied. Acute liver injury in HCT is often due to sinusoidal obstruction syndrome (previously known as venoocclusive disease), or acute GVHD. Liver dysfunction at later time posttransplantation may be associated with acute or chronic GVHD, iron overload, or other causes of hepatitis. Lung injury in HCT is multifactorial, and it remains crucially important to diagnose and treat pulmonary infections. The pulmonary biopsy yields clinically unsuspected diagnoses in the majority of cases and its utilization is likely to increase. The pathology of the skin and kidney in HCT patients are detailed in accompanying articles.