An unusual clinical finding and surgery for mediastinal histoplasmosis

Histoplasma capsulatum, a mycosis endemic to the United States, can lead to various clinical manifestations. In the presence of sequelae of histoplasmosis, such as mediastinal adenitis, granulomas, and fibrosing mediastinitis, surgical management may be an unexpected but necessary treatment. Due to the complexity of the mediastinum, it is imperative to have an optimal operative planning. In this report, we present an unusual case of an inflammatory mediastinal mass in the setting of acute histoplasmosis resulting in left atrial compression and arrhythmias.

Introduction

Histoplasma capsulatum, a mycosis endemic to the United States, can present with various clinical manifestations. Inhalation of airborne particles in the conidial state most often results in asymptomatic colonization of the lungs, although exposure can also trigger a robust inflammatory response manifesting as flu-like symptoms such as fever , shortness of breath, cough and weight loss. [1-3]. In most cases, acute pulmonary histoplasmosis is self-limiting. However, when necessary, treatment varies depending on the severity of the disease and the immune status of the patient. An oral regimen of itraconazole (six to 12 weeks) is the treatment usually prescribed when symptoms persist [4]. In the rare event that sequelae or complications related to histoplasmosis develop, surgery may be warranted in an attempt to relieve compression on the thoracic and mediastinal structures or relieve the obstruction. [5]. In this report, we present an unusual case of an inflammatory mediastinal mass in the setting of acute histoplasmosis resulting in left atrial compression and arrhythmias.

Presentation of the case

A 33-year-old man with a significant history of thyroid nodule presents with episodes of palpitations and chronic cough following a cave diving trip. The initial assessment consisted of medical management in case of suspected bronchitis and recent onset atrial fibrillation (Figure 1). The patient experienced debilitating palpitations and dizziness requiring multiple emergency room visits. The patient underwent radiofrequency ablation by extended circumferential ablation (WACA) to isolate the pulmonary veins and ablation of the cavotricuspid isthmus (CTI) to create a bidirectional CTI block, which briefly arrested the arrhythmias.

Nevertheless, the cough lingered and the palpitations returned with increasing severity. Pulmonary function tests were obtained indicating fixed upper airway obstruction. Imaging was obtained which identified a subcarinal soft tissue density of 3.4 cm on computed tomography (CT). The patient underwent bronchoscopy with a subcarineal lymph node biopsy, which revealed necrotic debris and the presence of rare organisms identified by Gram stain consistent with H.capsulatum. Treatment was started with itraconazole; however, debilitating episodes of palpitations and dizziness requiring recurrent emergency room visits persisted.

Cardiac magnetic resonance imaging (MRI) was obtained to further assess the mass. MRI showed a large posterior mediastinal mass located posterior to the right superior pulmonary vein, contiguous and compressing the superior-posterior aspect of the left atrium. Cardiac electrophysiologists conferred that the location of the mass was likely a focus for arrhythmias. Faced with signs of cardiac compression and the persistence of symptoms despite medical treatment, the patient was taken to the operating room for exploration, excision of the mass and to ensure the absence of additional pathology.

The procedure was started using a straight video assisted thoracoscopic approach (VATS) and a large inflammatory mass was identified in the subcarinal space. A careful dissection of the mass was initiated in an attempt to visualize the extent of the bulky lesion. However, due to the inability to properly visualize the posterior mediastinal space, the procedure was converted to a thoracotomy via a left posterolateral incision. On further visualization, the mass was found adherent to the right lower pulmonary vein, esophagus, pericardium, and right lung. After continued meticulous dissection, the mass was successfully removed and no further pericardial compression was observed.

After the operation, the patient recovered uneventfully in the cardiothoracic intensive care unit and was discharged with itraconazole on the third postoperative day. Final pathology demonstrated necrotizing granulomatous inflammation, a sequela of pulmonary histoplasmosis. Subsequently, the patient was discharged home and remains asymptomatic at one year of follow-up with no complications or resulting readmissions.

Discussion

H. capsulatum is an endemic mycosis in the river valleys of Mississippi and Ohio with an estimated incidence of 6.1 cases per 100,000 individuals [1]. Although most often presenting with flu-like symptoms, mediastinal manifestations such as adenitis, granulomas, or fibrosing mediastinitis are all potential complications that can lead to obstruction and compression of mediastinal structures requiring surgical intervention. . Most often, symptomatic presentations are the result of airway compression [1]. Hamoud et al. studied the complications of pulmonary histoplasmosis and found that hemoptysis and recurrent pneumonia were the main reasons for surgery [5]. In our patient, the development of left atrial compression and atrial fibrillation represents a unique sequela of histoplasmosis.

The complexity of the mediastinum makes imaging a necessity for diagnosis as well as precise delineation of mediastinal structures and compartments. In cases of mediastinal pathology, cross-sectional images generated by CT are useful for detecting cysts, fatty tissue, soft tissue masses, calcification, and air, which can aid in the creation of a differential diagnosis. [6]. MRI, although used less frequently, offers the possibility of visualizing the structures of the mediastinum more clearly, and should especially be used in cases of vascular involvement. [6]. In our case, CT imaging demonstrated a subcarinal soft tissue density of 3.4 cm; however, in the setting of persistent cardiac arrhythmia, an MRI was obtained to further characterize the mass and aid in operative planning.

Using a VATS approach for mediastinal surgery offers the advantages of decreased morbidity and recovery time compared to traditional thoracotomy [7]. However, exploration of the confined space of the posterior mediastinum may also limit the usefulness of VATS. [8]. A narrow working field with adherent or friable inflamed tissue can present serious challenges to the surgeon. In this case, the dense inflammatory tissue of the subcarinal mass limited the visual field requiring the creation of a left posterolateral thoracotomy. Expanded exposure visualized adhesion of the mass to the right lower pulmonary vein, esophagus, pericardium, and right lung, facilitating successful surgery.

conclusion

In conclusion, histoplasmosis can lead to various clinical manifestations. In the presence of sequelae of histoplasmosis, such as mediastinal adenitis, granulomas and fibrosing mediastinitis, surgical treatment may be an unexpected but necessary treatment. Due to the complexity of the mediastinum, it is imperative to have an optimal operative planning. When dense inflamed tissue is encountered, particularly in narrow areas such as the posterior mediastinum, early conversion to open thoracotomy should be considered to improve exposure to the operative field and facilitate the safe performance of the operative procedure.

Christine E. Phillips