Pulmonary histoplasmosis: Unusual histopathologic findings

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.

Anti-Interferon Autoantibodies in Adult-Onset Immunodeficiency Syndrome and Severe COVID-19 Infection

Adult-onset immunodeficiency syndrome due to anti-interferon (IFN)-γ autoantibodies has attracted much attention in recent years. It usually occurs in previously healthy people and usually presents as chronic, recurrent, and hard-to-control infections that can be effectively treated with aggressive antibiotic therapy. Adult-onset immunodeficiency syndrome is also referred to as AIDS-like syndrome. Anti-type I IFN (IFN-I) autoantibodies have been reported to play a significant role in the pathogenesis of coronavirus disease 2019 (COVID-19) and preexisting anti-IFN-I autoantibodies are associated with an increased risk of severe COVID-19. This review summarizes the effects of anti-IFN autoantibodies on the susceptibility and severity of various infectious diseases, including SARS-CoV-2 infection. In addition, we discuss the role of anti-IFN autoantibodies in the pathogenesis of autoimmune diseases that are characterized by recurrent infections.

Paediatric Histoplasmosis 2000-2019: A Review of 83 Cases

Histoplasmosis is an endemic fungal infection that is confined to specific geographical regions. Histoplasma spp. are primary pathogens that cause disease in both immunocompetent and immunocompromised patients, ranging from a single-organ (mostly affecting the lungs) infection to life-threatening disseminated disease. Knowledge about the clinical epidemiology relies on data from adult populations; little is known about the patient and disease characteristics in the paediatric population. Therefore, a structured review of published cases of paediatric histoplasmosis between 2000 and 2019 was performed. A literature search of PubMed was conducted and the epidemiological and clinical data from 83 cases were analysed. The mean age at presentation was 9.5 ± 5.5 years, and 51% were girls. Two-thirds of the children were immunocompromised. The majority of children presented with disseminated disease. The most frequently observed clinical symptoms were respiratory symptoms, alongside non-specific systemic features, including fever, myalgia, fatigue and weight loss. The mortality rate was 11%. Histoplasmosis affects children of any age. Being immunocompromised is a risk factor for severe and disseminated disease. The lack of specific presenting features leads to underreporting and delay in diagnosis. To improve the recognition and outcome of histoplasmosis in childhood, increased awareness and surveillance systems are warranted.

Infectious Lung Disease

Infectious diseases are one of the main causes of morbidity and mortality worldwide. With new pathogens continuously emerging, known infectious diseases reemerging, increasing microbial resistance to antimicrobial agents, global environmental change, ease of world travel, and an increasing immunosuppressed population, recognition of infectious diseases plays an ever-important role in surgical pathology. This becomes particularly significant in cases where infectious disease is not suspected clinically and the initial diagnostic workup fails to include samples for culture. As such, it is not uncommon that a lung biopsy becomes the only material available in the diagnostic process of an infectious disease. Once the infectious nature of the pathological process is established, careful search for the causative agent is advised. This can often be achieved by examination of the hematoxylin and eosin-stained sections alone as many organisms or their cytopathic effects are visible on routine staining. However, ancillary studies such as histochemical stains, immunohistochemistry, in situ hybridization, or molecular techniques may be needed to identify the organism in tissue sections or for further characterization, such as speciation.

Immunology of fibrotic lung disease: managing infections whilst preventing autoimmunity?

Interstitial lung disease (ILD) and lung fibrosis are characterized by different grades of fibrosis and inflammation. Persistent low-grade inflammation is believed to play a major pathogenic role, leading to an imbalance of cytokines, growth factors, and tissue proteinases. Recruited monocytes and macrophages play a pivotal role through their cytokine expression and possibly differentiation into fibrocytes, pericytes, or myofibroblasts. Atypical bacterial infections can cause ILD, although not usually in the form of usual interstitial pneumonia. On the other hand, bacterial colonization is frequently encountered in patients with chronic fibrotic lung disorders, and patients regularly undergo antibacterial treatment. As demonstrated in patients with diffuse panbronchiolitis and other chronic respiratory disorders, treatment with macrolides can be beneficial. This is partly explained by their antimicrobial effects but, for macrolides, immunomodulatory properties have been identified which might also be beneficial in patients with ILD or lung fibrosis. This article reviews the immunology of lung fibrogenesis and putative implications of macrolides for reinstallation of tolerance.

Role of microorganisms in interstitial lung disease

PURPOSE OF REVIEW

To review the role of microorganisms in interstitial lung disease (ILD) and to emphasize their importance in initiation and course of ILD.

RECENT FINDINGS

ILD can be idiopathic but often causality such as drugs or connective tissue disease can be found. Multiple microorganisms have been associated with ILD. On the one hand, pulmonary infection can cause extensive pulmonary damage with patterns of an ILD. On the other hand, microorganisms can trigger the immune system and provoke an abnormal response- not directed against the causative pathogen- that may result in ILD. Moreover, patients with ILD often are susceptible to infection, and infections can importantly influence the course of ILD. Furthermore, not only an infection but also its treatment can result in a drug-induced pneumonitis, eventually resulting in long-term lung damage.

SUMMARY

Microorganisms can initiate and/or influence the course of ILD. Early recognition, adequate diagnostic evaluation and therapy are essential to prevent permanent damage. Prevention of infection in patients with established ILD is strongly recommended.

Histoplasmosis: a study of 158 cases in Venezuela, 2000-2005

Histoplasmosis, a granulomatous disease caused by Histoplasma capsulatum, is endemic in Venezuela. We conducted the current study to appraise retrospectively the demographic data, clinical features, diagnostic methods, and treatment of patients with histoplasmosis from January 2000 to December 2005. We reviewed the medical records of outpatient cases with a diagnosis of histoplasmosis and considered clinical samples processed at our laboratory. We collected demographic, epidemiologic, and clinical data from each case as available, including results of any mycologic examinations performed. Treatment and outcome data were available for some patients. We assessed 158 cases of histoplasmosis: 103 (65.2%) patients came from the Caracas metropolitan area; 53 were associated with acquired immunodeficiency syndrome (AIDS), 14 with tuberculosis, and 8 with paracoccidioidomycosis. Six pediatric patients were malnourished. Epidemiologic data suggested histoplasmosis in most cases. Patients received treatment with itraconazole and/or amphotericin B. Our results may reflect changes in the epidemiology occurring in Venezuela, perhaps due to environmental changes and the presence of AIDS. Several mycologic exams are necessary to ensure a proper diagnosis. More reliable data and statistics on this infection are necessary to monitor outbreaks closely and to establish if there is an epidemic pattern.