Fibrosing mediastinitis (FM), which is also known as mediastinal fibrosis or sclerosing mediastinitis, is an uncommon, benign and progressive condition. What is Fibrosing Mediastinitis? Medistinal fibrosis is the common, but most severe, late complication of Histoplasmosis. Many Physicians believe mediastinal. Idiopathic Fibrosing Mediastinitis. Questions posed and edited by Candace McIntosh and Lucille Enix Reponses by James Loyd, M.D.. What are the symptoms.

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Fibrosing mediastinitis is the least common, but the most severe, late complication of histoplasmosis. Many physicians believe fibrosing mediastinitis to be the result of an abnormal immunologic response to antigens released by the soil-based fungus histoplasma capsulatum. It should be differentiated from the many other less-severe mediastinal complications of histoplasmosis, and from other causes fibroding fibrosing mediastinitis, which are termed idiopathic fibrosing mediastinitis.

Idiopathic fibrosing mediastinitis is even less common, but may have multiple causes, none of which are related to histoplasmosis. Accordingly, there are two types of fibrosing mediastinitis; histoplasmosis-related fibrosing mediastinitis, and idiopathic fibrosing mediastinitis which may have multiple causes unrelated to histoplasmosis.

Both types are rare disorders caused by proliferations of collagen, fibrosis tissue and associated inflammatory cells within the mediastinum the space between the lungs. Post histoplasmosis fibrosing mediastinitis is characterized by invasive, calcified fibrosis centered at locations of lymph nodes, which, by definition, occludes major vessels or airways.

Often symptoms of fibrosing mediastinitis do not develop until the disease has progressed to a level at which there is damage to some vessel or organ, usually due to insufficient blood flow because of an obstructed vessel.

Symptoms may appear suddenly, even though the scar progressed slowly for months or years, because the scar growth itself causes no symptoms. When scar has developed in a major vessel to the extent that it restricts blood flow to or from a lung, the decreased blood flow may cause lung infarction, with pain of pleurisy.

Histoplasmosis is due to the most common endemic parasitic fibroing in the United States, Histoplasma capsulatum. In the mediastinitos area, along the Mississippi and Ohio River valleys, nearly all persons are infected in childhood. Histoplasmosis also occurs in isolated spots around the world, but is most common in North and Central America, with isolated cases reported from Southeast Asia and Africa.

Pulmonary infection is dibrosing asymptomatic or only mildly symptomatic in the infected person. Some infected persons may suffer flu-like symptoms. It flourishes in soil fertilized by bird droppings, and is carried in bat guano, although birds themselves are not infected with H.

However, chickens are known to harbor the organism in their feathers. Chicken houses and bat guano under bridges and their environs are notorious sources of H. Histoplasmosis has also been found in urban settings and is occasionally referred to as an urban disease as well.

In urban settings where the soil is disturbed, the fungus spores become air borne. The University of Texas Southwest Medical Center reported between and cases of Histoplasma infection during a year period when buildings were under construction.

Although a bird sanctuary existed in the area, most cases occurred in employees who had no direct contact with the sanctuary.

The spores were drawn into buildings through air conditioning systems. An outbreak of histoplasmosis occurred in students in a junior high school in Ohio. On Earth Day, a courtyard was raked and swept, and fibrosjng entire school building was contaminated with air containing Histoplasma spores. The epidemic was short-lived and influenza-like. Inbird droppings swept from the roof of a courthouse in Arkansas were distributed through the building by window air-conditioners.

Overall, histoplasmosis is considered usually to be an asymptomatic and clinically insignificant infection. In the vast majority of the many millions of infected persons, infection and recurrent infection follow a generally benign course. The number of persons with the severe complication, fibrosing mediastinitis, is a small fraction, estimated to total only a few hundred in the US, of the millions of individuals infected by histoplasmosis. It is not known why some individuals are predisposed to excessive immune response to the organism, which leads to excessive scarring and obstruction of major vessels or airways mwdiastinitis characterizes FM.

They persist for years, maybe indefinitely, and may release antigen to stimulate an ongoing immune response. Calcification of the infected lymph nodes is typical, but may require years to develop.

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Rarely calcified stones broncholith may work their way into airways, and may be coughed out, or they may cause bronchial obstruction and infection. Typically, people with fibrosing mediastinitis were originally infected with H. There is no evidence that there is a preferred ethnic origin or gender disparity.

Patients with histoplasmosis-related fibrosing mediastinitis present with signs of fatigue, shortness of breath dyspneacough with blood hemoptysis or without, chronic chest pleuritic pain and recurrent pulmonary infection. Superior vena cava syndrome, the swelling that develops in some patients due to obstruction of the vena fibrosiing, is a common symptom.

Fibrosing Mediastinitis | FAQ

Some patients do not have the syndrome, despite having obstruction of the SVC, if collateral alternative veins sometimes visible on the anterior chest enlarge sufficiently to return blood to the heart. Cough and shortness of breath are fibroslng most common symptoms when obstruction of the central airways occurs. Pulmonary venous obstruction usually presents with shortness of breath and coughing blood hemoptysis.

Symptoms can be present for years before diagnosis. Patients with idiopathic fibrosing mediastinitis may present symptoms of fever, chills, sweats, shortness of breath, cough and chest pain. They may also have fibrosis elsewhere in the body which may cause symptoms at those other sites. Although the fungus resides in the soil, and the fungus mediastiniits fertilized by bird droppings, birds are not themselves infected.

Spores become airborne when the soil is disturbed, and birds and bats also transport the spores. Idiopathic fibrosing mediastinitis is not related to histoplasmosis.

It has been reported in the setting of autoimmune disease, Behcet disease, Wegeners granulomatosis, IgG4 disease, rheumatic fever, radiation therapy, severe viral infections of coxsackie B, or trauma.

In addition, it can occur in association with other idiopathic fibroinflammatory disorders at sites outside the chest, including retroperitoneal fibrosis, sclerosing cholangitis, Riedel thyroiditis, pseudotumor of the orbit, and others. Reliable prevalence information is not available, but the affected population of histoplasmosis-related fibrosing mediastinitis is estimated to be several hundred people in the United States. Post histo FM is seen only in individuals who lived in an endemic region sometime during their life.

The number of persons with idiopathic fibrosing mediastinitis is estimated to be several dozen in the United States.

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Symptoms of the following disorders can be similar to, or caused by, fibrosing mediastinitis. Understanding of each condition may be critical for correct diagnosis. Superior vena cava syndrome occurs as a result of occlusion of the superior vena cava vessel, which may also happen from other causes, mediastihitis as central intravenous catheters. The symptoms that arise from this condition often lead to the diagnosis of fibrosing mediastinitis.

In addition, signs of right heart failure may be prominent. Mediastinal granuloma MG is a different late complication from histoplasmosis, but can be confused with fibrosing mediastinitis. Mediastinal granuloma affects the mediastinal lymph nodes and causes substantial enlargement of the lymph nodes.

Fibrosing mediastinitis is comprised meciastinitis solid fibrotic scar, whereas Mediastinal Granuloma is comprised of semiliquid contents with a thin capsule. The enlargement of Mediastinal Granuloma may occasionally cause compression of the airways or SVC, especially in young children, and possibly displacement of the esophagus. Mediastinal granuloma can also be caused by mycobacteria, so tuberculosis testing should be performed in patients at risk for it.

Symptoms may include fatigue and dyspnea, or pain while swallowing. In the past it was thought that mediastinal granuloma would eventually progress to fibrosing mediastinitis but the best evidence now supports that they are separate conditions. Surgical resection is the most effective therapy mediastiniits symptomatic mediastinal granuloma, and surgery in FM is high risk and rarely of therapeutic value in FM, so if a radiologist incorrectly diagnoses FM, that can delay or prevent appropriate surgery for MG.

Diagnosing either form of fibrosing mediastinitis is best accomplished by chest CT, a scan that shows the abnormal tissue in the mediastinum the space between the lungs. Sometimes surgical biopsy of the abnormal tissue in the mediastinum is needed to exclude malignancy such as a lymphoma, especially if the CT scan shows that the tissue does not have calcification, which is a hallmark sign of FM which complicates prior histoplasmosis. If the patient has occlusion of the vena cava and there are collateral veins that have developed, the superior mediastinum may be widened on imaging studies.


Pulmonary venous obstruction may lead to pulmonary hypertension. A magnetic resonance angiography MRA of the mediasginitis can be helpful in special circumstances, especially to evaluate the pulmonary veins where they enter the left atrium.

Diagnosis in many cases is delayed, often for many firosing because symptoms are not specific. Erroneous initial diagnoses include asthma, pneumonia, chronic obstructive lung disease, pulmonary embolism with lung infarction, and, in a few, mitral stenosis and congestive heart failure, a symptom complex produced by obstruction of the pulmonary veins as they enter the left atrium.

The current widespread use of CT of the chest has greatly figrosing detection and diagnosis of FM. There is no standard therapy for either form of meciastinitis mediastinitis. The natural history of Idiopathic FM is not known, but there are reports of individual patients who had a pharmacologic response fibrising spontaneous improvement, which has not been seen with post Histoplasmosis FM. Currently there are no drugs identified that will stop the histoplasmosis-related fibrous meduastinitis from growing.

Because the scar of post Histoplasmosis FM grows very slowly in most patients, treatment would be needed for many years or decades to be effective. Reports of individual patients describe treatment of patients with idiopathic fibrosing mediastinitis with the following drugs: Data is not available about the effectiveness of these treatments, and most reports are individual cases, so it is not possible to be sure whether a response was actually caused by the treatment.

When fluid retention occurs, patients are treated with diuretic therapy, which may require supplementing potassium. Antibiotics can be used to treat complications such as pneumonia and chest infections. Corticosteroids such as prednisone appear to provide benefit for some patients, but can also cause serious side effects.

Regular exercise is beneficial for heart and muscle function, and is encouraged for all patients as tolerated. Successful treatment of post histoplasmosis FM generally uses a mechanical approach, because there are no well documented responses to any pharmacologic agent. When FM patients cough blood, catheterization of the aorta to perform bronchial artery embolization is effective to block the arteries that are the source of bleeding in most patients.

This procedure is available by interventional radiologists in most major medical centers. FM can block the airways or the vessels going to, or returning from the lungs.

When structures of only one lung are blocked, it can cause pain or coughing blood, but most patients do reasonably well long-term, as long as the contralateral lung has no problem. When structures of both lungs are affected, this can be serious and life threatening, so catheterization with stenting Albers to restore flow in some vessels may benefit many patients.

Blockage of the superior vena cava requires no treatment unless there are symptoms, but if there is swelling of the arms and neck, associated headache or other symptoms then stenting or bypass should be considered.

Itraconazole is an oral antifungal treatment which is often used for patients who have fibrosing mediastinitis due to histoplasma, but there is no evidence it helps.

Fibrosing Mediastinitis – NORD (National Organization for Rare Disorders)

Antifungal therapies are not shown to change medixstinitis course for FM, which is more related to ongoing reaction of the immune system, rather than growth of organisms. Regardless, a trial is commonly used because FM can kediastinitis a serious problem, and itraconazole is generally safe.

If the scar tissue in FM is localized, surgical resection has been used rarely, but is high risk and appropriate for very few patients. This is not a preferred method of treatment and should only be used in the most extreme cases due to a high level of morbidity and mortality. The mortality rates for fibrosing mediastinitis fibrozing on the form and its extent.

Idiopathic fibrosing mediastinitis has not been well studied, but appears to rarely be life threatening. The mortality of post histoplasmosis FM is substantial in individuals who have critical structures obstructed in both lungs. Patients who have lost function of one lung can do surprisingly well for many years or decades, as long as the other lung has no problem.