Bronchocentric granulomatosis

# Overview
Bronchocentric granulomatosis is not a disease per se but a histopathological finding of the bronchi and bronchioles that is believed to be a nonspecific response to airway injury. It is commonly seen in association with asthma and allergic bronchopulmonary aspergillosis, but can also be observed in non-asthmatics with no identifiable etiological agent.

# Historical Perspective
- Bronchocentric granulomatosis was first discovered by Liebow, in 1973.

# Classification
- There are two patterns observed in Bronchocentric granulomatosis, the more common pattern is observed in young men with asthma and less common pattern is seen in older patients who are non-asthmatic. 

# Pathophysiology
- The exact pathophysiology of Bronchocentric granulomatosis is not known.
- On microscopic histopathological analysis, there is central necrotizing granulomatous inflammation of the bronchi and bronchioles.

# Causes
- Bronchocentric granulomatosis can be idiopathic or caused by other diseases including asthma and allergic bronchopulmonary aspergillosis. 
- A number of other diseases have been associated with Bronchocentric granulomatosis such as fungal infections, rheumatoid arthritis, ankylosing spondylitis and glomerulonphritis.

# Differentiating Bronchocentric granulomatosis from other Diseases
- Bronchocentric granulomatosis needs to be differentiated from other lung diseases that present with solitary or multiple nodules and consolidation.
- The differential diagnosis of Bronchocentric granulomatosis has to be made from other granulomatous lung diseases and can be divided into infectious and noninfectious diseases:
- Some infectious causes include:
- Mycobacteria i.e. mycobacterium tuberculosis
- Fungi i.e Histoplasma
- Parasites i.e Dirofilaria
- A few noninfectious diseases include:
- Sarcoidosis
- Hypersensitive pneumonitis
- Aspiration pneumonia 

# Epidemiology and Demographics
- The incidence and prevalence of Bronchocentric granulomatosis is not known.

## Age
- Patients of all age groups may develop Bronchocentric granulomatosis.

## Gender
- Bronchocentric granulomatosis affects men and women equally.

## Race
- There is no racial predilection for Bronchocentric granulomatosis.

# Diagnosis

## Symptoms
- Bronchocentric granulomatosis usually presents with nonspecific symptoms. Symptoms can vary in individuals who have asthma and those who do not. Pulmonary symptoms such as cough, dyspnea and pleuritic chest pain are more common in asthmatic.
- Additional symptoms that the patient may present with can be due to the coexisting disease. For example: those with allergic bronchopulmonary aspergillosis may present with symptoms such as fever, malaise and expectoration of brownish mucus plugs.

## Laboratory Findings
- The nonspecific laboratory tests that can favour the diagnosis of Bronchocentric granulomatosis include:
- Complete and differential blood count - counts are typically raised in infective processes.
- Total Serum IgE levels - (Around half of the cases of Bronchocentric granulomatosis are associated with allergic bronchopulmonary aspergillosis, hence, Serum IgE levels can be measured as a nonspecific test which may indicate a suspicion towards ABPA). 
- Sputum cultures - to rule out mycobacterial and fungal infections
- Other investigations are conducted to rule out possible associated diseases. For example, if systemic rheumatic disease is suspected, tests such as rheumatoid factor, anti-citrullinated peptide antibodies and anti-neutrophil cytoplasmic antibody are carried out.

## Imaging Findings
- Radiologically Bronchocentric granulomatosis is represented by nodules, which may be single or multiple, most commonly found near the upper lobes.
- CT is the imaging modality of choice for Bronchocentric granulomatosis.
- On CT, Bronchocentric granulomatosis is characterized by focal mass or lobar consolidation with atelectasis.

## Other Diagnostic Studies
- Bronchocentric granulomatosis may also be diagnosed using open lung biopsy.
- Findings on open lung biopsy include necrotizing granulomatous inflammation of the bronchi and bronchioles with presence of lymphocytes, macrophages and neutrophils.
- Histopathological picture usually reveals the destruction of the walls of the bronchi and bronchioles, and the replacement of these structures with granulomatous tissue. Necrotic debris is often seen in the lumens of the airway.
- It is important to note that the surrounding vessels are not affected. This differentiates it from other conditions which do effect the vessels as in the case of Wegener's granulomatosis. 
- Bronchoalveolar lavage can show underlying fungal, bacterial or neoplastic cells that may be present. 

# Treatment

## Medical Therapy
- The mainstay of therapy for Bronchocentric granulomatosis is corticosteroids.
- It has been observed in some individuals, that idiopathic Bronchocentric granulomatosis, may resolve spontaneously with out any medical therapy. 
- Any coexisting disease should be treated with their usual course of management i.e. an anti fungal agent should be given if there is an underlying fungal infection.
- Lobectomy may be an option in some cases, in fear of bronchogenic carcinoma,  but it shows no added benefit to the medical therapy. 

## Prevention
- There are no primary preventive measures available for Bronchocentric granulomatosis.