Pulmonary, mediastinal, and cardiac presentations of histoplasmosis

Genotypic diversity, virulence, and molecular genetic tools in Histoplasma

SUMMARYHistoplasmosis is arguably the most common fungal respiratory infection worldwide, with hundreds of thousands of new infections occurring annually in the United States alone. The infection can progress in the lung or disseminate to visceral organs and can be difficult to treat with antifungal drugs. Histoplasma, the causative agent of the disease, is a pathogenic fungus that causes life-threatening lung infections and is globally distributed. The fungus has the ability to germinate from conidia into either hyphal (mold) or yeast form, depending on the environmental temperature. This transition also regulates virulence. Histoplasma and histoplasmosis have been classified as being of emergent importance, and in 2022, the World Health Organization included Histoplasma as 1 of the 19 most concerning human fungal pathogens. In this review, we synthesize the current understanding of the ecological niche, evolutionary history, and virulence strategies of Histoplasma. We also describe general patterns of the symptomatology and epidemiology of histoplasmosis. We underscore areas where research is sorely needed and highlight research avenues that have been productive.

Pulmonary Histoplasmosis Complicated by Nonvalvular Right Ventricular Wall Histoplasma capsulatum Endocarditis

Histoplasmosis is commonly a self-limited fungal disease that primarily affects the lung and reticuloendothelial system. Cardiac involvement by histoplasmosis is uncommon. In this report, we provide a detailed description of severe pulmonary histoplasmosis complicated by the disease involvement of the free wall of the right ventricle. A 55-year-old female presented with cough, fevers, dyspnea, and 30-pound unintentional weight loss in 6 months. Her past medical history was significant for supraventricular tachycardia with permanent pacemaker implantation. Imaging studies revealed an intracardiac mass accompanied by mediastinal lymphadenopathy and bilateral lung nodules. Endobronchial ultrasound-guided transbronchial needle aspiration of station 4R lymph nodes revealed numerous yeast forms, morphologically consistent with Histoplasma capsulatum. The diagnosis was further corroborated by the elevated titers of serum antibodies against Histoplasma capsulatum. The right ventricular mass debulking with biopsy showed necrotizing granulomatous inflammation involving nonvalvular endocardium and myocardium of the free wall of the right ventricle. The report documents an unusual presentation of pulmonary histoplasmosis accompanied by nonvalvular endocarditis and suggests a possible association between the site of the cardiac infection and the presence of a permanent intravascular pacer device.

Pericardial effusion in an immunocompetent host- a unique presentation of histoplasmosis

Histoplasma capsulatum infection is infrequently considered in the differential diagnoses for acute pericarditis in immunocompetent hosts when presenting with tamponade physiology, given its gradual infective nature. We describe a case of a young male presenting solely with acute pericarditis with pericardial effusion and early cardiac tamponade physiology secondary to a pulmonary histoplasmosis infection. Our patient had no pulmonary symptoms; the only pulmonary manifestation of histoplasmosis included incidental findings of subcarinal lymphadenopathy and a left lingular nodule abutting the pericardium. Given failure of symptom improvement with pericardiocentesis and first-line therapy for idiopathic/viral pericarditis, further workup of the pulmonary nodule was pursued. Histopathologic analysis of tissue showed caseating granulomas and fungal Grocott-Gömöri's methenamine silver stain revealed yeast consistent with Histoplasma species. The patient improved with itraconazole therapy.

Learning objective

Pulmonary histoplasmosis has potential to present as a pericardial effusion in the immunocompetent individual. In addition to pericardiocentesis, antifungal therapy can be curative.

Catheter-based intervention for pulmonary vein stenosis due to fibrosing mediastinitis: The Mayo Clinic experience

Introduction

Fibrosing mediastinitis (FM) is a rare but fatal disease characterized by an excessive fibrotic reaction in the mediastinum, which can lead to life-threatening stenosis of the pulmonary veins (PV). Catheter-based intervention is currently the only viable option for therapy. However, the current literature on how best to manage these difficult cases, especially in regards to sequential interventions and their potential complications is very limited.

Methods

We searched through a database of all patients who have undergone PV interventions at the Earl H. Wood Cardiac Catheterization Laboratory in Mayo Clinic, Rochester. From this collection, we selected patients that underwent PV intervention to relieve stenosis secondary to FM.

Results

Eight patients were identified, with a mean age of 41 years (24–59 years). Five were men, and three were women. Three patients underwent balloon angioplasty alone, and five patients had stents placed. The majority of patients had acute hemodynamic and symptomatic improvement. More than one intervention was required in five patients, four patients had at least one episode of restenosis, and four patients died within four weeks of their first PV intervention.

Conclusions

We describe the largest reported case series of catheter-based intervention for PV stenosis in FM. Although catheter-based therapy improved hemodynamics, short-term vascular patency, and patient symptoms, the rate of life-threatening complications, restenosis, and mortality associated with these interventions was found to be high. Despite these associated risks, catheter-based intervention is the only palliative option available to improve quality of life in severely symptomatic patients with PV stenosis and FM. Patients with PV stenosis and FM (especially those with bilateral disease) have an overall poor prognosis in spite of undergoing these interventions due to the progressive and recalcitrant nature of the disease. This underscores the need for further innovative approaches to manage this disease.

Pseudomediastinal fibrosis caused by massive lymphadenopathy in domestically acquired particulate lung disease

In this report, we describe a case of domestically acquired particulate lung disease (DAPLD) or "hut lung" in a 59-year-old woman of Moroccan descent who emigrated to the Netherlands, having lived in an rural area for most her life. She presented with obstructive lung disease and with signs of mediastinal fibrosis which were shown to be caused by massive enlargement of mediastinal lymph nodes. To the best of our knowledge, this is the first case of DAPLD from Morocco and the first report of a case of DAPLD mimicking mediastinal fibrosis.

Histoplasmose pulmonar aguda: relato de uma microepidemia

Os autores relatam uma microepidemia de histoplasmose pulmonar, com cinco crianças que desenvolveram a doença em um período de 7 a 14 dias após a limpeza de um forno desativado para produção de carvão vegetal. Todas apresentaram quadro de febre alta persistente, tosse seca, astenia e anorexia, com 28 dias de evolução. Quando buscaram atendimento médico, uma delas encontrava-se taquipnéica, febril, com hepatomegalia e palidez cutânea, estando as restantes em regular estado geral e já sem febre. As radiografias de tórax demonstravam, em todos os casos, infiltrados reticulonodulares grosseiros, difusos e bilaterais, além de linfonodomegalias hilares. As tomografias computadorizadas evidenciaram pequenos nódulos difusos, com distribuição aleatória, além das linfonodomegalias. Os diagnósticos foram confirmados por meio da imunodifusão em gel para Histoplasma capsulatum, que foi positiva em todas as amostras pareadas coletadas com 15 dias de intervalo. Apenas uma criança necessitou de internação, por causa de importante queda no estado geral, sendo realizado tratamento de suporte e observação. Todas as crianças evoluíram com melhora clínica, sem o uso de antifúngicos, e foram submetidas a tomografias de controle após cerca de 50 dias, que demonstraram importante regressão das lesões.

Acute Histoplasmosis in Spelunkers Returning from Mato Grosso, Peru

Background: Histoplasmosis is a fungal disease with a worldwide distribution. Travelers returning from endemic areas with a history of exposure to fungal spores have a high risk of infection. Methods: We report four cases of acute pulmonary disease in Italian spelunkers returning from Mato Grosso, Peru. Results: Symptoms and radiologic findings were consistent with acute pulmonary illness. Laboratory data supported the hypothesis of histoplasmosis. Conclusions: Histoplasmosis should be considered in the differential diagnosis in travelers returning from endemic areas, who report a risk of exposure, and present with respiratory illness. In this setting, seroconversion may be considered diagnostic of pulmonary histoplasmosis.

Clinical manifestation of mediastinal fibrosis and histoplasmosis

We treated 20 patients thought to have mediastinal fibrosis secondary to Histoplasma capsulatum. All but 1 were symptomatic. The most common symptoms were dyspnea (8), hemoptysis (6), postobstructive pneumonia (5), and superior vena caval obstruction (2). Nine patients had severe stenosis of the trachea, carina, or main bronchus. Special stains identified Histoplasma capsulatum in surgical specimens in 9 patients. Surgical procedures were done for 18 of 20 patients (resection of subcarinal mass, 6; right middle and lower lobectomy, 5; carinal pneumonectomy, 4; esophagoplasty, 4; sleeve resection, 3 (with right main bronchus in 1, right lower and middle lobectomy in 1, and carina in 1); right upper lobectomy, 1; middle lobectomy, 1; and bronchoplasty of left main bronchus, 1. There were 4 deaths, 3 after complications of carinal pneumonectomy and 1 in a patient with tracheobronchial obstruction that could not be dilated. Two patients were treated with amphotericin and 4 with ketoconazole. Sclerosing mediastinitis secondary to histoplasmosis presents tremendous surgical challenges because of the intense fibrosis encountered. Bronchoplastic procedures are possible in spite of the intense fibrosis. High mortality rates after carinal resection may be encountered. The exact role of antifungal therapy is as yet undefined.

Left recurrent laryngeal nerve paralysis: an unusual presentation of histoplasmosis

A case of histoplasmosis seen as left recurrent laryngeal nerve paralysis in a 49-year-old man is described. The patient had roentgenographic findings of a solitary, noncalcified left upper lobe mass and mediastinal adenopathy. Tissue diagnosis of histoplasmosis was obtained using a thoracotomy, allowing institution of appropriate treatment.

Surgical implications of sclerosing mediastinitis. A report of six cases and review of the literature

Sclerosing mediastinitis is an uncommon disease associated with a multiplicity of clinical syndromes. The cause of this disorder is probably an abnormal fibroproliferative response to an inflammatory stimulus, most commonly a granulomatous infection secondary to Histoplasma capsulatum. The pathophysiology of this disease is predicated on the encasement of mediastinal vital organ structures within a dense fibrotic mass. This mass appears to emanate from an invasive chronic inflammatory process causing erosion as well as external compression of these structures. The following case reports illustrate the diversity of this disease entity, representing a patient population from the Ohio River Valley, endemic for histoplasmosis. The purpose of this report is to elucidate the various clinical manifestations of sclerosing mediastinitis and to correlate the pathologic process with a rational approach to treatment.

Surgical intervention in histoplasmosis

Histoplasmosis is a ubiquitous disease in endemic areas that has a generally subclinical course. Excessive inflammatory response may bring some patients to the attention of a thoracic surgeon to exclude malignancy of a noncalcified pulmonary or mediastinal mass or to relieve compression of specific structures. Mediastinal granuloma or fibrosing mediastinitis may involve the superior vena cava, pulmonary vessels, heart and pericardium, tracheobronchial tree, or esophagus. The cases of 94 recently treated patients are presented as well as a review of the American surgical literature. The current use of computed tomography, the time and extent of operative intervention, and the role of antifungal therapy are important to an overall understanding of the surgical treatment of the manifestations of histoplasmosis.

Pulmonary vascular occlusion and fibrosing mediastinitis

Patients with fibrosing mediastinitis causing obstruction of pulmonary veins and arteries may present with many of the historic, physical, and laboratory findings of patients with pulmonary hypertension due to chronic thrombotic obstruction of major pulmonary arteries. Because the latter is subject to surgical correction, and the former is not, it is important to differentiate between the two and to be aware of the similarities in presentation. Three patients with pulmonary hypertension due to compression of pulmonary veins and the right pulmonary artery by fibrosing mediastinitis are presented who illustrate these points. A review of the literature documents other instances in which vascular involvement due to fibrosing mediastinitis has mimicked other types of pulmonary hypertension.