What is Fibrosing Mediastinitis?
Fibrosing Mediastinitis is a pathological condition which is stated to be a rare but the most severe form of complication arising from histoplasmosis. It is highly believed that Fibrosing Mediastinitis arises due to abnormal immunologic response to antigens released by the fungus histoplasma capsulatum which is found in abundance in the soil around us. Fibrosing Mediastinitis can also be caused with a history of histoplasmosis. Such a type of Fibrosing Mediastinitis is termed as idiopathic Fibrosing Mediastinitis and is much more obsolete.
Fibrosing Mediastinitis is basically caused by proliferations of collagen, fibrosis tissue, and associated inflammatory cells within the mediastinum. Fibrosing Mediastinitis remains asymptomatic unless the disease has progressed to an advanced stage where there is significant damage to a muscle or an organ for which the main cause is decreased blood flow as a result of obstruction caused by a damaged vessel. Scar tissue build up which is very variable being very slow in some individuals and very rapid is some also gives rise to symptoms. If there is excessive scar tissue build up around a vessel to such an extent that there is decreased blood flow to and from the lungs then it may result in conditions like lung infarction and pleurisy.
What are the Causes of Fibrosing Mediastinitis?
As stated above, Fibrosing Mediastinitis is a rare complication of histoplasmosis and develops due to the abnormal immune reaction to the exposure of the fungus Histoplasma capsulatum. This fungus is found in the soil in the areas around Mississippi and Ohio River valleys. This fungus is present in soil and is fertilized by bird droppings. As soon as the soil containing the fungus is disturbed, these spores become airborne thus spreading the infection histoplasmosis which in turn causes Fibrosing Mediastinitis.
Fibrosing Mediastinitis caused due to other factors and not related to histoplasmosis is called as idiopathic Fibrosing Mediastinitis and has been related to medical conditions like Behcet Disease, Wegener’s granulomatosis, rheumatic fever, viral infections caused due to coxsackie B virus, and even in some cases trauma to the mediastinal region. In some cases, Fibrosing Mediastinitis can also occur due to inflammatory disorders like retroperitoneal fibrosis and sclerosing cholangitis.
What are the Symptoms of Fibrosing Mediastinitis?
An individual with Fibrosing Mediastinitis may have come in contact with the fungus in childhood itself but the symptoms of Fibrosing Mediastinitis present themselves when the individual is between 20 to 40 years of age. Some of the symptoms of Fibrosing Mediastinitis are:
- Severe fatigue
- Shortness of breath
- Pleuritic chest pain
- Recurrent pulmonary infection
- Chills and sweats.
These symptoms basically occur when one of the main vessels like the superior vena cava, the vessel of the airways, pulmonary arteries get affected due to Fibrosing Mediastinitis. Another symptom due to Fibrosing Mediastinitis is swelling of the superior vena cava.
How is Fibrosing Mediastinitis Diagnosed?
The best way to diagnose Fibrosing Mediastinitis whether it is caused due to histoplasmosis or it is idiopathic is by taking a CT scan of the chest. The CT scan of the chest will show abnormal tissue in the mediastinum. A perfusion nuclear medicine scan is the best way to pinpoint the location of any reduced blood flow around the mediastinal region and also to confirm whether there is adequate blood flow to and from the lung in some cases, a biopsy is required to rule out any malignancy especially if the abnormal tissue does not have calcification shown on the CT scan. The above tests are sufficient enough to diagnose Fibrosing Mediastinitis.
The problem with Fibrosing Mediastinitis is that the symptoms present themselves so late that the diagnosis is always delayed until there is significant damage already done to the vessels or organs. Fibrosing Mediastinitis can be erroneously diagnosed as pneumonia, COPD, pulmonary or embolism but with the use of CT of the chest the diagnosis of Fibrosing Mediastinitis can now be definitively made.
What is the Treatment for Fibrosing Mediastinitis?
Fibrosing Mediastinitis does not have a successful response to any pharmacologic treatment as of yet and hence treatment is based on improving the symptoms. For cases of hemoptysis due to Fibrosing Mediastinitis, a bronchial artery embolization procedure can be done and is found to be very successful in treating hemoptysis due to Fibrosing Mediastinitis.
Another complication of Fibrosing Mediastinitis is blockage of airways which go and come from the lungs. If vessels of one lung get affected then the patient may not have a problem but when both the lungs get affected that is when complications arise which can be potentially serious. This can be treated with stenting and catheterization. For cases where the superior vena cava gets blocked and result in symptoms like swelling of the neck and arms, headaches etc., then stenting or a bypass surgery may be required for treatment. Fibrosing Mediastinitis caused due to histoplasmosis can also be treated using an antifungal agent called Itraconazole. Studies have shown that antifungal agents are somewhat effective and they do halt the progression of Fibrosing Mediastinitis in any way. Localized scar tissues formed due to Fibrosing Mediastinitis can be removed surgically but this is a highly complex procedure and is done rarely.
What is the Prognosis of Fibrosing Mediastinitis?
The overall prognosis for Fibrosing Mediastinitis depends on the extent and severity of the disease process. Not much study has been done on Idiopathic Fibrosing Mediastinitis but this condition is not considered as life threatening. Prognosis of patients with Fibrosing Mediastinitis whose both lungs get affected and blocked have a much guarded prognosis due to the complexity of the condition but if only one lung is affected then the prognosis is very surprisingly very good for patients suffering from Fibrosing Mediastinitis.