Introduction

Fibrosing mediastinitis is a rare condition which affects the mediastinum. The mediastinum is defined as the area in the centre of your chest that houses your heart, lungs, large blood vessels, and windpipe. Due to the fairly rare nature of the condition, its aetiology and prevalence are difficult to determine; however, there is a study showing that across 33 existing cases, most were females aged between 13 to 65.¹ The purpose of this article is to help you recognise how to identify fibrosing mediastinitis, how it is diagnosed, and how it is managed. This article also aims to differentiate other possible conditions that may present similarly to fibrosing mediastinitis. 

What is fibrosing mediastinitis?

When breaking down the term fibrosing mediastinitis, ‘fibrosing’ suggests the formation of scar tissue and the ‘-itis’ in ‘mediastinitis’ is suggestive of inflammation of the mediastinum. True to its name, the physiological process behind fibrosing mediastinitis involves rapid cell division of the fibrous tissue within the mediastinum. There are two types: granulomatous and non-granulomatous.² 

Granulomatous fibrosing mediastinitis involves granulomas forming secondary to the body’s immune system working to keep a chronic condition or an infection under control. The most common infections that result in granulomatous fibrosing mediastinitis are histoplasmosis and tuberculosis.³ 

Non-granulomatous fibrosing mediastinitis occurs as a reaction to radiation exposure, certain drugs such as methysergide, or some autoimmune conditions, like primary sclerosing cholangitis or retroperitoneal fibrosis.² 

Clinical presentation

The formation of scar tissue in fibrosing mediastinitis causes the narrowing of structures and organs within the mediastinum, namely blood vessels and the lungs. The result included the following symptoms:⁴ 

• Shortness of breath
• Chest pain
• Decreased stamina
• Tiredness
• Headaches
• Coughing up blood
• Chest infections
• Difficulty swallowing
• Swelling of the arms, chest and face

The swelling of the arms, face, and chest may be a result of the narrowing of the superior vena cava (SVC). The SVC is one of the two major blood vessels that pour blood back into the heart after it has travelled around the body so that it may be sent to the lungs to be re-oxygenated. Narrowing of the SVC will cause blood to back up into the neck and for it to be pushed into surrounding smaller blood vessels in the chest area, hence resulting in swelling. It can also result in the coughing up of blood, difficulty swallowing, and shortness of breath.⁵

Constrictive pericarditis may also manifest as a rare secondary condition resulting from the narrowing of vessels in fibrosing mediastinitis. Some patients may experience neurological symptoms resulting from compression of the laryngeal or phrenic nerves.² 

Due to its status as a rare condition and the non-specific nature of its symptoms, fibrosing mediastinitis is typically diagnosed after ruling out other conditions and conducting diagnostic tests.

Diagnostic techniques

Diagnostic techniques may include:

• Chest X-ray -  A chest X-ray may show widening of the mediastinum and enlarged lymph nodes which may cause narrowing of the windpipe and its extension into the lungs known as bronchi and hilum. This is typical of granulomatous fibrosing mediastinitis
• Contrast-enhanced computed tomography (CT) scan -  A contrast-enhanced CT scan is the imaging tool of choice for fibrosing mediastinitis as it is more detailed than a plain chest x-ray. It can be used to assess the degree of narrowing of the structures within the lungs and the surrounding major vessels 
• CT angiography - Conducting a CT angiography can also help visualise the extent of blockage inflicted upon the blood vessels within the mediastinum
• Magnetic resonance imaging (MRI) - An MRI scan can also be used to assess the level of lymph node enlargement in the lymph nodes surrounding the hilar and mediastinal regions. However, as MRI does not always reliably depict the level of fibrosis, it is favoured second to contrast-enhanced CT in the diagnosis of fibrosing mediastinitis 

Treatment and management

At the moment, there is no curative treatment for fibrosing mediastinitis. The two main treatment strategies available are therapeutic and surgical. 

Therapeutic management involves the use of corticosteroids to suppress the immune system so that it is no longer working against the body rather than for it. 

Surgical interventions can be used when therapeutic management has proven insufficient. However, it is reserved only for when the disease can be localised, and surgical intervention will give symptomatic relief. It is contraindicated when both sides of the mediastinum are involved as there is a high risk of mortality. Surgical procedures to open narrowed areas can include trans-oesophageal, endovascular, or endo-bronchial balloon stenting.⁶

What other mediastinal disorders could be mistaken for fibrosing mediastinitis? 

Mediastinal tumours 

A mediastinal tumour is a mass on the mediastinum that can be benign (non-cancerous, does not spread, has well-defined borders) or malignant (cancerous, can spread, and has erratic borders difficult to differentiate from healthy tissue).⁷ Examples include:

• Thymomas
• Lymphomas
• Germ cell tumours
• Neurogenic tumours 

Although mediastinal tumours and fibrosing mediastinitis share many symptoms such as chest pain, shortness of breath, and coughing up of blood, they can be differentiated in that weight loss and anaemia are more commonly seen in patients with malignant tumours. Benign tumours and fibrosing mediastinitis should be differentiated with diagnostic tools such as imaging and biopsies. Additionally, mediastinal tumours occur most commonly in people aged between 30-50.

Inflammatory and infectious mediastinal disorders 

As iterated above, the term ‘mediastinitis’ refers to inflammation of the mediastinum. This can occur without accompanying fibrosis, such as in the following conditions:

• Acute mediastinitis
• Chronic mediastinitis
• Sarcoidosis 

Sudden inflammation of the mediastinum, such as in acute mediastinitis, can occur as a result of trauma to the area, for example after an endoscopy or due to forceful vomiting. Chronic inflammation, such as in chronic mediastinitis, can occur for unknown reasons or as a result of a pre-existing infection such as tuberculosis or a fungal infection.⁸ Similar to fibrosing mediastinitis, sarcoidosis can also present with granulomas, shortness of breath, chest pain, and swollen lymph nodes. However, unlike fibrosing mediastinitis, sarcoidosis is often accompanied by pulmonary hypertension (high blood pressure in and around the lungs).⁹ 

Vascular mediastinal disorders 

Vascular mediastinal disorders include the blood vessels inside the mediastinum such as:

• Thoracic aortic aneurysm
• Aortic dissection 

Both thoracic aortic aneurysms and aortic dissection share symptoms such as chest pain, difficulty swallowing, and shortness of breath with fibrosing mediastinitis. However, in thoracic aortic aneurysms, the pain is sharp and sudden, and patients can also experience low blood pressure and loss of consciousness.¹⁰ In aortic dissections, patients will experience sharp and sudden pain with potential paralysis and dizziness, which are not common to fibrosing mediastintis.¹¹

Miscellaneous conditions 

There are a few other conditions that can be mistaken for fibrosing mediastinitis that do not fall under any of the previous categories such as mediastinal cysts and lymphadenopathy.

Mediastinal cysts are cysts in the mediastinum that occur during development and patients are born with them. Symptoms are very similar to fibrosing mediastinitis, such as chest pain and difficulty breathing.¹² 

Lymphadenopathy is the general term for swollen lymph nodes which may look similar in appearance to the swelling that occurs in fibrosing mediastinitis, especially in the neck or chest.¹³ 

Summary

Fibrosing mediastinitis involves the formation of extensive scar tissue within the mediastinum that can cause occlusion of the structures within the mediastinum and subsequent complications. Symptoms are generalised and can be mistaken for other conditions such as mediastinal tumours, infectious mediastinal conditions, inflammatory mediastinal conditions, vascular mediastinal conditions, and a couple of other miscellaneous conditions such as mediastinal cysts and lymphadenopathy. Fibrosing mediastinitis should be diagnosed after ruling out other conditions and by using the appropriate diagnostic imaging modalities.