Search

Connective tissue diseases are a heterogeneous group of autoimmune diseases that can affect a variety of organ systems. Lung parenchymal involvement is an important contributor to morbidity and mortality in children with connective tissue disease. Connective tissue disease-associated lung disease in children often manifests as one of several radiologic-pathologic patterns of disease, with certain patterns having a propensity to occur in association with certain connective tissue diseases. In this article, key clinical, histopathologic, and computed tomography (CT) features of typical patterns of connective tissue disease-associated lung disease in children are reviewed, with an emphasis on radiologic-pathologic correlation, to improve recognition of these patterns of lung disease at CT and to empower the pediatric radiologist to more fully contribute to the care of pediatric patients with these conditions., (© 2024. The Author(s).)

Pulmonary alveolar microlithiasis is an autosomal recessive lung disease caused by a deficiency in the pulmonary epithelial Npt2b sodium-phosphate co-transporter that results in accumulation of phosphate and formation of hydroxyapatite microliths in the alveolar space. The single cell transcriptomic analysis of a pulmonary alveolar microlithiasis lung explant showing a robust osteoclast gene signature in alveolar monocytes and the finding that calcium phosphate microliths contain a rich protein and lipid matrix that includes bone resorbing osteoclast enzymes and other proteins suggested a role for osteoclast-like cells in the host response to microliths. While investigating the mechanisms of microlith clearance, we found that Npt2b modulates pulmonary phosphate homeostasis through effects on alternative phosphate transporter activity and alveolar osteoprotegerin, and that microliths induce osteoclast formation and activation in a receptor activator of nuclear factor-κB ligand and dietary phosphate dependent manner. This work reveals that Npt2b and pulmonary osteoclast-like cells play key roles in pulmonary homeostasis and suggest potential new therapeutic targets for the treatment of lung disease., (© 2023. The Author(s).)

Pulmonary alveolar microlithiasis (PAM) is a fascinating rare lung disease that is associated with the accumulation of hydroxyapatite microliths within the lumen of the alveolar spaces. In most patients, PAM is discovered incidentally on radiographs performed for other purposes, and the typical disease course is characterised by slowly progressive respiratory insufficiency over decades. Recent genetic analyses that have revealed that the deficiency of the sodium-phosphate cotransporter NPT2B is the cause of PAM have enabled the development of powerful animal models that inform our approach to disease management and treatment. Here we review the epidemiology and molecular pathophysiology of PAM, as well as the diagnostic approach, clinical manifestations, radiographic and pathologic features, and clinical management of the disease. Although there are no proven treatments for PAM, progress in our understanding of disease pathogenesis is providing insights that suggest strategies for trials., Competing Interests: Conflict of interest: P. Kosciuk has nothing to disclose. Conflict of interest: C. Meyer has nothing to disclose. Conflict of interest: K. Wikenheiser-Brokamp has nothing to disclose. Conflict of interest: F.X. McCormack has nothing to disclose., (Copyright ©ERS 2020.)

Pulmonary Langerhans cell histiocytosis (PLCH) is a rare smoking-related lung disease characterized by dendritic cell (DC) accumulation, bronchiolocentric nodule formation, and cystic lung remodeling. Approximately 50% of patients with PLCH harbor somatic BRAF-V600E mutations in cells of the myeloid/monocyte lineage. However, the rarity of the disease and lack of animal models have impeded the study of PLCH pathogenesis. Here, we establish a cigarette smoke-exposed (CS-exposed) BRAF-V600E-mutant mouse model that recapitulates many hallmark characteristics of PLCH. We show that CD11c-targeted expression of BRAF-V600E increases DC responsiveness to stimuli, including the chemokine CCL20, and that mutant cell accumulation in the lungs of CS-exposed mice is due to both increased cellular viability and enhanced recruitment. Moreover, we report that the chemokine CCL7 is secreted from DCs and human peripheral blood monocytes in a BRAF-V600E-dependent manner, suggesting a possible mechanism for recruitment of cells known to dominate PLCH lesions. Inflammatory lesions and airspace dilation in BRAF-V600E mice in response to CS are attenuated by transitioning animals to filtered air and treatment with a BRAF-V600E inhibitor, PLX4720. Collectively, this model provides mechanistic insights into the role of myelomonocytic cells and the BRAF-V600E mutation and CS exposure in PLCH pathogenesis and provides a platform to develop biomarkers and therapeutic targets.

Diffuse cystic lung diseases (DCLDs) are a group of diverse pulmonary disorders with varying pathophysiology that are characterized by the presence of thin-walled, air-filled spaces within lung parenchyma. High-resolution computed tomography plays a crucial role in the evaluation of DCLDs, and cyst characteristics such as morphology, distribution, and the presence of other associated radiologic findings can help distinguish between different DCLDs. DCLDs can be classified according to their underlying pathophysiology as neoplastic, genetic, lymphoproliferative, infectious, associated with other forms of interstitial lung disease, or related to smoking. In this review we will provide a clinical overview on the most common DCLDs that are encountered in clinical practice: lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, Birt-Hogg-Dubé syndrome, and lymphoid interstitial pneumonia/follicular bronchiolitis, with a focus on practical aspects that can help clinicians in the optimal diagnosis and management of patients with DCLDs., (Copyright © 2020 by Daedalus Enterprises.)

Exposure to cigarette smoke can lead to a variety of parenchymal lung diseases, including diffuse cystic lung diseases (DCLDs). Lymphangioleiomyomatosis (LAM) is the prototypical DCLD and has a characteristic appearance on high-resolution CT (HRCT). We present a series of four patients with DCLD on HRCT who were referred to our institution with a presumed diagnosis of LAM and who were found instead to have smoking-related injury of the small airways on histopathological analysis. We submit that cigarette smoke-induced small airway injury can present as DCLD on HRCT in a pattern that can mimic LAM. A detailed history of cigarette smoke exposure should be obtained in patients presenting with DCLD, and imaging features should not be used in isolation to establish a firm diagnosis of LAM., (Copyright © 2018 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.)

Interstitial lung diseases, especially lymphoproliferative disorders such as follicular bronchiolitis and lymphoid interstitial pneumonia, are commonly seen in association with Sjögren syndrome. Although the predominant computed tomographic (CT) findings in patients with lymphoid interstitial pneumonia/follicular bronchiolitis include poorly defined centrilobular nodules and ground-glass attenuation, cystic changes can be seen in approximately two-thirds of these patients. The objective of this study was to define the clinical, radiological, and histopathological features of cyst-predominant lymphoid interstitial pneumonia/follicular bronchiolitis in patients with Sjögren syndrome. We present four patients who were referred to our institution with diffuse cystic changes on chest CT imaging. All four had a presumptive diagnosis of lymphangioleiomyomatosis but were subsequently found to have Sjögren syndrome. The diagnosis was established based on the clinical symptoms of xerostomia and xerophthalmia along with serologic detection of antinuclear antibodies, rheumatoid factor, anti-Sjögren's syndrome-related antigen A (SSA)/Ro antibodies, and anti-Sjögren's syndrome-related antigen B (SSB)/La antibodies. The cystic pattern associated with Sjögren syndrome had a characteristic appearance on chest CT images. Typical features included a wide variation in cyst size, internal structure within cysts, geographic simplification of parenchymal architecture producing a "dissolving lung appearance," perivascular and often basilar-predominant distribution, and frequent association with ground-glass opacities and nodules. In a compatible clinical context, we submit that these findings can be sufficiently distinctive to obviate the need for lung biopsy, even in the absence of confirmatory serological studies or lip biopsy. Clinicians should consider occult Sjögren syndrome in the differential diagnosis of patients presenting with idiopathic diffuse cystic lung disease.

Pulmonary alveolar microlithiasis (PAM) is a rare, autosomal recessive lung disorder associated with progressive accumulation of calcium phosphate microliths. Inactivating mutations in SLC34A2, which encodes the NPT2b sodium-dependent phosphate cotransporter, has been proposed as a cause of PAM. We show that epithelial deletion of Npt2b in mice results in a progressive pulmonary process characterized by diffuse alveolar microlith accumulation, radiographic opacification, restrictive physiology, inflammation, fibrosis, and an unexpected alveolar phospholipidosis. Cytokine and surfactant protein elevations in the alveolar lavage and serum of PAM mice and confirmed in serum from PAM patients identify serum MCP-1 (monocyte chemotactic protein 1) and SP-D (surfactant protein D) as potential biomarkers. Microliths introduced by adoptive transfer into the lungs of wild-type mice produce marked macrophage-rich inflammation and elevation of serum MCP-1 that peaks at 1 week and resolves at 1 month, concomitant with clearance of stones. Microliths isolated by bronchoalveolar lavage readily dissolve in EDTA, and therapeutic whole-lung EDTA lavage reduces the burden of stones in the lungs. A low-phosphate diet prevents microlith formation in young animals and reduces lung injury on the basis of reduction in serum SP-D. The burden of pulmonary calcium deposits in established PAM is also diminished within 4 weeks by a low-phosphate diet challenge. These data support a causative role for Npt2b in the pathogenesis of PAM and the use of the PAM mouse model as a preclinical platform for the development of biomarkers and therapeutic strategies., (Copyright © 2015, American Association for the Advancement of Science.)

The diffuse cystic lung diseases have a broad differential diagnosis. A wide variety of pathophysiological processes spanning the spectrum from airway obstruction to lung remodeling can lead to multifocal cyst development in the lung. Although lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis are perhaps more frequently seen in the clinic, disorders such as Birt-Hogg-Dubé syndrome, lymphocytic interstitial pneumonia, follicular bronchiolitis, and light-chain deposition disease are increasingly being recognized. Obtaining an accurate diagnosis can be challenging, and management approaches are highly disease dependent. Unique imaging features, genetic tests, serum studies, and clinical features provide invaluable clues that help clinicians distinguish among the various etiologies, but biopsy is often required for definitive diagnosis. In part II of this review, we present an overview of the diffuse cystic lung diseases caused by lymphoproliferative disorders, genetic mutations, or aberrant lung development and provide an approach to aid in their diagnosis and management.

The diffuse cystic lung diseases (DCLDs) are a group of pathophysiologically heterogenous processes that are characterized by the presence of multiple spherical or irregularly shaped, thin-walled, air-filled spaces within the pulmonary parenchyma. Although the mechanisms of cyst formation remain incompletely defined for all DCLDs, in most cases lung remodeling associated with inflammatory or infiltrative processes results in displacement, destruction, or replacement of alveolar septa, distal airways, and small vessels within the secondary lobules of the lung. The DCLDs can be broadly classified according to underlying etiology as those caused by low-grade or high-grade metastasizing neoplasms, polyclonal or monoclonal lymphoproliferative disorders, infections, interstitial lung diseases, smoking, and congenital or developmental defects. In the first of a two-part series, we present an overview of the cystic lung diseases caused by neoplasms, infections, smoking-related diseases, and interstitial lung diseases, with a focus on lymphangioleiomyomatosis and pulmonary Langerhans cell histiocytosis.