INTRODUCTION: Fibrosing mediastinitis is a rare disorder characterized by invasive proliferation of fibrotic tissue and dense collagen deposition within the mediastinum. In the US it most commonly occurs in areas endemic for histoplasmosis (prevalence 1:100.000) [1-2]. Clinical symptoms reflect compression and obstruction of mediastinal structures. Fibrosing mediastinitis affects predominantly young adults and is associated with substantial morbidity and mortality . Herein we report a case of rapidly developing non-calcified fibrosing mediastinitis associated with histoplasmosis resulting in pulmonary venous obstruction.
CASE PRESENTATION: A 27-year-old woman presented with an 8 months history of dyspnea, cough and wheezing. Outside chest radiography revealed a right middle lobe infiltrate refractory to levofloxacin therapy. Chest CT showed bilateral ground glass infiltrates predominantly involving the right lower lobe, a small right pleural effusion, and extensive hilar and mediastinal lymphadenopathy.(FIG.1A,B) Mediastinoscopy demonstrated reactive lymphadenopathy. It was complicated by transient post-procedural hypotension. Transthoracic echocardiography revealed pulmonary hypertension (right ventricular systolic pressure 69 mmHg), with right ventricular dysfunction, dilatation and hypertrophy. Chest CT scan with pulmonary embolism protocol showed no pulmonary emboli. Subsequently, paroxysmal nocturnal dyspnea, orthopnea and peripheral edema developed. She was a never smoker from Wisconsin, without occupational exposures, HIV risk factors or history of substance abuse. Examination showed respiratory distress, blood pressure 118/70 mmHg, heart rate 115 beats/min, 84% oxygen saturation on room air, elevated jugular venous pressure, crackles in the right lung base, accentuated P2, 2/6 systolic murmur and 1+ pitting lower extremity edema bilaterally. The patient was hospitalized and bronchoscopy with transbronchial needle aspiration of subcarinal lymphadenopathy showed edematous mucosa but was otherwise non-diagnostic. Hypoxemia and hypotension during and following the bronchoscopy required ICU admission, mechanical ventilation and vasopressor support. Chest radiograph revealed pulmonary edema. Histoplasmosis titer by complement fixation was 1:8. Hemodynamic assessment disclosed: pulmonary artery pressure of 89/45 mmHg, wedge pressure of 38 mmHg, and cardiac index of 1.3 L/min/m2. Epoprostenol, nitric oxide and dobutamine were carefully administered, but ineffective. Transesophageal echocardiography and chest CT with contrast showed obstruction of the right inferior and left superior pulmonary veins, severe stenosis of the right superior and a patent left inferior pulmonary vein.(FIG.1C-E) Only the 90% stenosed right superior pulmonary vein was accessible to balloon angioplasty. Successful recanalization via right heart catheterization resulted in initial hemodynamic improvement but the patient continued to require vasopressors and died on the ninth hospital day. Autopsy confirmed severe pulmonary edema with venous infarcts and pulmonary venous obstruction caused by dense fibrosis consistent with fibrosing mediastinitis. Old necrotic granulomas with fungi consistent with Histoplasma (evaluated with silver stain) were also identified. (FIG.2A-C).
DISCUSSIONS: In the US, most cases of fibrosing mediastinitis are attributed to histoplasmosis and considered to represent late complications in susceptible individuals[1,2]. In the absence of a tissue diagnosis, Histoplasmosis associated fibrosing mediastinitis is clinically diagnosed in patients presenting with slowly progressive invasion and/or compression of mediastinal structures by localized, almost universally calcified mediastinal mass lesions[1,2]. Diffuse non-calcified mediastinal infiltration is typically encountered in the less common idiopathic form of fibrosing mediastinitis which is associated with retroperitoneal fibrosis, orbital pseudotumor, Riedel's thyroiditis and methysergide therapy. Our case illustrates that Histoplasmosis associated fibrosing mediastinitis may present as rapidly progressive diffuse infiltration of the mediastinum compromising vital structures even in the absence of radiographic calcifications and convincing serologic evidence of Histoplasmosis. In the absence of effective medical therapy, percutaneous and surgical interventions to relieve mechanical obstructions remain the most beneficial interventions.
CONCLUSION: Current clinical criteria used to separate fibrosing mediastinitis associated with Histoplasmosis from idiopathic variants do not reliably distinguish between these entities.
DISCLOSURE: Tobias Peikert, None.