Inflammatory bowel disease in Hermansky-Pudlak syndrome: a retrospective single-centre cohort study.

BACKGROUND: Knowledge about inflammatory bowel disease (IBD) in patients with Hermansky-Pudlak syndrome (HPS), a rare autosomal recessive disorder characterized by defective biogenesis of lysosome-related organelles, could provide insights into IBD in general. OBJECTIVE: To expand the understanding of IBD in patients with HPS. METHODS: Retrospective review of records from patients with HPS evaluated at the National Institutes of Health Clinical Center from 1995 to 2019 was conducted. Clinical features of IBD, genotyping results and histologic findings of colectomy specimens were analysed. RESULTS: IBD affected 37 (14.2%; 12 male, 25 female) of 261 patients with HPS. Median age of onset was 17 years; range was 1 to 52 years. The most common symptoms of HPS IBD were hematochezia, abdominal pain and loose stools. Fistulae or extra-intestinal manifestations developed in 30% or 22%, respectively. Genotyping showed that patients with biallelic variants in HPS1, HPS3, HPS4 or HPS6 were diagnosed with IBD. Six children had very early-onset IBD. Patients with HPS-3 had mild manifestations of IBD. Medical therapy and bowel resection were utilized to treat 73% and 35% of patients with HPS IBD, respectively; 7 of 13 patients receiving anti-tumor necrosis factor alpha therapy had prolonged clinical responses. Active cryptitis, chronic inflammatory changes, granulomas and ceroid lipofuscinosis were histopathologic findings in three colectomy specimens. CONCLUSIONS: IBD resembling Crohn's disease affects some patients with HPS; genetic heterogeneity is a feature of HPS IBD. HPS3 is a new gene associated with human IBD. Very early-onset IBD can develop in HPS.

Erdheim-Chester disease: a rare multisystem histiocytic disorder associated with interstitial lung disease.

Erdheim-Chester disease (ECD) is a rare multisystem histiocytosis syndrome of unknown cause that usually affects adults. Histiocytic infiltration of multiple end organs produces bone pain, xanthelasma and xanthoma, exophthalmos, diabetes insipidus, and interstitial lung disease. Differential diagnosis includes Langerhans cell histiocytosis, metabolic disorders, malignancy, and sarcoidosis. ECD can be diagnosed using a combination of clinical and histopathologic findings. Sites of involvement include lung, bone, skin, retroorbital tissue, central nervous system, pituitary gland, retroperitoneum, and pericardium. Symmetrical long bone pain with associated osteosclerotic lesions, xanthomas around the eyelids, exophthalmos, and/or diabetes insipidus suggest ECD. Approximately 35% of patients have associated lung involvement, characterized by interstitial accumulations of histiocytic cells and fibrosis in a predominantly perilymphangitic and subpleural pattern. This pattern distinguishes ECD from other histiocytic disorders involving the lung. The diagnosis is confirmed by tissue biopsies that contain histiocytes with non-Langerhans cell features. In general, the clinical course of patients with this disease varies, and the prognosis can be poor despite treatment. Clinical trials for treatment of ECD have not been conducted and treatment is based on anecdotal experience.

Potential pathogenesis and clinical aspects of pulmonary fibrosis associated with rheumatoid arthritis.

Pulmonary fibrosis is an extra-articular disorder that can occur in association with rheumatoid arthritis. The differential diagnosis of this disorder is similar to that of idiopathic pulmonary fibrosis, but specific entities such as atypical pulmonary infections and drug-induced interstitial lung disease must be considered as causes of pulmonary fibrosis in patients with rheumatoid arthritis. Although the cause of lung fibrosis in persons with rheumatoid arthritis is unknown, factors that can potentially contribute to the pathogenesis of this pulmonary disease include genetic susceptibility, development of an altered immunologic response, and/or aberrant host repair processes. The clinical course of patients with pulmonary fibrosis and rheumatoid arthritis is heterogeneous but is generally insidious, chronic, and progressive. These patients respond unpredictably to available empiric therapeutic agents and, overall, their prognosis is poor; limited data suggests that the median survival time can be less than 4 years.

TRAIL expression in vascular smooth muscle.

TRAIL is a cell-associated tumor necrosis factor-related apoptosis-inducing ligand originally identified in immune cells. The ligand has the capacity to induce apoptosis after binding to cell surface receptors. To examine TRAIL expression in murine vascular tissue, we employed in situ hybridization and immunohistochemistry. In these studies, we found that TRAIL mRNA and protein were specifically localized throughout the medial smooth muscle cell layer of the pulmonary artery. Notably, a similar pattern of expression was observed in the mouse aorta. Consistent with these findings, we found that cultures of primary human aorta and pulmonary artery smooth muscle cells express abundant TRAIL mRNA and protein. We also found that these cells and endothelial cells undergo cell lysis in response to exogenous addition of TRAIL. Last, we confirmed that TRAIL specifically activated a death program by confirming poly(ADP ribose) polymerase cleavage. Overall, we believe that these findings are relevant to understanding the factors that regulate cell turnover in the vessel wall.

Airway epithelial Fas ligand expression: potential role in modulating bronchial inflammation.

Epithelium-derived Fas ligand is believed to modulate inflammation within various tissues. In this paper, we report findings that suggest a similar immunoregulatory role for Fas ligand in the lung. First, Fas ligand was localized to nonciliated, cuboidal airway epithelial cells (Clara cells) throughout the airways in the normal murine lung by employing nonisotopic in situ hybridization and immunohistochemistry. Second, gld mutant mice, which express a dysfunctional Fas ligand protein, were noted to develop prominent infiltration of inflammatory cells in submucosal and peribronchial regions of the upper and lower airways. Third, during allergic airway inflammation induced by ovalbumin in mice, cell-associated staining for Fas ligand mRNA and protein was markedly reduced in the airway epithelium. These data suggest that Clara cell-derived Fas ligand may control immune activity in the airway; thus alterations in this protective mechanism may be involved in the pathogenesis of certain inflammatory conditions of the airway, such as asthma.

Fas expression in pulmonary alveolar type II cells.

Fas, a type I membrane receptor protein, transduces a signal culminating in apoptosis after binding to the Fas ligand. Information regarding the expression of Fas in nonlymphoid tissues, although limited, suggests a role for Fas in epithelial progenitor cell populations. In this paper, we provide several lines of evidence indicating that the progenitor cell of the alveolus, the type II cell, displays restricted expression of Fas. We found 1) Fas gene expression in RNA derived from fresh isolates of primary rat type II cells; 2) restriction of Fas expression to a subset of alveolar type II cells by in situ hybridization and immunohistochemistry of the normal mouse lung; 3) induction of apoptosis in a mouse lung type II epithelial cell line (MLE) after activation of Fas; and 4) induction of apoptosis in a subpopulation of type II cells after the intratracheal instillation of an activating anti-Fas antibody in mice. These findings suggest that Fas-dependent apoptosis is involved in regulating turnover of the alveolar epithelium.

Simultaneous in situ hybridization and TUNEL to identify cells undergoing apoptosis.

Apoptotic cells in tissue sections can be localized by in situ labelling of partly degraded DNA. In a heterogeneous population of cells, however, the specific identity of cell types undergoing apoptosis often cannot be reliably achieved at the light microscope level because of the marked alterations in cellular morphology that characterize apoptosis. In order to clearly specify cell types undergoing apoptosis, in situ end labelling has been coupled to immunohistochemistry. This method is limited by the availability of antibodies that bind to cell-specific protein markers in tissue sections. In contrast, we describe a method that combines in situ end labellin with in situ hybridization, a technique that specifies cell types based on mRNA expression. Taking advantage of the specific expression of surfactant protein C mRNA in type II alveolar epithelial cells, we demonstrate that this technique has the ability to localize alveolar type II cells undergoing apoptosis in vivo after the intratracheal instillation of an antibody that activates the cell surface Fas protein. The wide availability of cell-specific gene markers suggests that this method can be adapted to define cell types that undergo apoptosis during various physiological and pathological states in vivo.