Pneumonitis

**Pneumonitis** is an inflammation of lung tissue due to factors other than microorganisms. Those can be radiation therapy of the chest, exposure to medications used during chemo-therapy, the inhalation of debris (e.g., animal dander) of food particles during vomiting, herbicides or fluorocarbons and some systemic diseases.

It is distinguished from pneumonia on the basis of causation as well as its manifestation since pneumonia can be described as pneumonitis combined with consolidation and exudation of lung tissue due to infection with microorganism. Pneumonitis is a respiratory inflammatory infection that affects the airways of the lungs from the basic reaction of inhalation. This includes any pathogens which could affect the lungs, including pulmonary fibrosis which causes lung scarring. Many people confuse pneumonia and having pneumonitis as the same thing, but there is a fine distinction between the two. Pneumonitis being the encapsulation of all respiratory infections which incorporates pneumonia and pulmonary fibrosis as major diseases while pneumonia is a localized infection. With any infection, the body has an immune response system. For most infections, that immune response is enough to control and apprehend the infection within a couple days, but if the tissue and the cells can't fight off the infection, the creation of pus will begin to form in the lungs which then hardens into lung abscess or suppurative pneumonitis. Patients that are immunodeficient and don't get treated immediately for any type of respiratory infection may lead to more severe infections and/or death.

## Causes

Alveoli are the primary structure affected by pneumonitis. Any particles that are smaller than 5 microns can enter the alveoli of the lungs. These tiny air sacs facilitate the passage of oxygen from inhaled air to the bloodstream. In the case of pneumonitis, it is more difficult for this exchange of oxygen to occur since irritants have caused inflammation of the alveoli. Due to the lack of a definitive determination of a single irritant causing pneumonitis, there are several possible causes.

* Viral infection. Measles can cause severe pneumonitis, and ribavirin has been proposed as a possible treatment. CMV is another cause.
* Pneumonia
* Radiation therapy
* Inhaling chemicals, such as sodium hydroxide
* Interstitial lung disease
* Sepsis
* Adverse reaction to medications
* Hypersensitivity to inhaled agents
* Inhalation of spores of some species of mushroom (bronchoalveolar allergic syndrome)
* Mercury exposure
* Smoking
* Overexposure to chlorine
* Bronchial obstruction (obstructive pneumonitis or post-obstructive pneumonitis)
* Ascariasis (during parasite migration)

Aspirin overdose, some antibiotics, and chemotherapy drugs have the potential to cause pneumonitis.

“Farmer’s lung” and “hot tub lung” are common names for types of hypersensitivity pneumonitis that result from exposure to some types of thermophilic actinomyces, mycobacteria and molds.

Avian proteins in bird feces and feathers can also cause pneumonitis.

Whole body or chest radiation therapy used for cancer treatment can result in pneumonitis.

Pneumonitis causes and triggers:

Lungs filled with white blood cells and at most times fluid

Inflammation makes it harder for lungs to pass oxygen into the bloodstream and inflammation and infection increases.

Triggers include: mold, bacteria, fungi, chemicals, animal fur, bird feathers, humidifiers, dust, plastic, and electronics.

## Diagnosis

A chest X-ray or CT is necessary to differentiate between pneumonitis and pneumonia of an infectious etiology. Some degree of pulmonary fibrosis may be evident in a CT which is indicative of chronic pulmonary inflammatory processes. Diagnosis of Pneumonitis is often difficult as it depends on a high degree of clinical suspicion when evaluating a patient with a recent onset of a possible interstitial lung disease. In addition, interpreting pathologic and radiographic test results remains a challenge to clinicians. Pneumonitis is often difficult to recognize and discern from other interstitial lung diseases.

Diagnostic procedures currently available include:

Evaluation of patient history and possible exposure to a known causative agent

High-Resolution Computed Tomography (HRCT) consistent with pneumonitis

Bronchoalveolar lavage with lymphocytosis

Lung biopsy consistent with pneumonitis histopathology

Exposure to causative agents of pneumonitis in a specific environment can be confirmed through aero/microbiologic analysis to verify its presence. Subsequent testing of patient serum for evidence of serum specific IgG antibodies confirms patient exposure.

Clinical tests include chest radiography or (HRCT) which may show centrilobular nodular and ground-glass opacities with air-trapping in the middle and upper lobes of the lungs. Fibrosis may also be evident. Bronchoalveolar Lavage (BAL) findings coinciding with pneumonitis typically include a lymphocytosis with a low CD4:CD8 ratio.

Histological samples of lung tissue with pneumonitis include the presence of poorly formed granulomas or mononuclear cell infiltrates. The presence of bronchocentric lymphohistiocytic interstitial pneumonia with chronic bronchiolitis and non-necrotising granulomas coincides with pneumonitis.

Since pneumonitis manifests in all areas of the lungs, imaging such as chest x-rays and Computerized tomography (CT) scans are useful diagnostic tools. While pneumonia is a localized infection, pneumonitis is widespread. A spirometer may also be used to measure pulmonary function.

During external examination, clubbing (swelling of fingertip tissue and increase in angle at the nail bed), and basal crackles may be observed.

For hypersensitivity pneumonitis many diagnosis take place through the focus of blood test, chest x-rays, and depending on severity of infection doctors may recommend a bronchoscopy.

Blood test are important to early detect for other causative substances that could eliminate possible causes of the hypersensitivity pneumonitis.

## Symptoms:

Shortness of breath, and sometimes a dry cough, are the most frequently reported results of pneumonitis.

Other symptoms may include malaise, fever, and dyspnea. Symptoms usually appear a few hours after exposure and peak at approximately eighteen to twenty-four hours.

Without proper treatment, pneumonitis may become chronic pneumonitis, resulting in fibrosis of the lungs and its effects: difficulty breathing, food aversion, and lethargy.

Patients also feel flushed, have discolored skin (blue or purple), sweat and take smaller and faster inhalations and undergo similar symptoms as the flu.

End-stage fibrosis and respiratory failure eventually lead to death in cases without proper management of chronic pneumonitis.

Acute hypersensitivity pneumonitis - development of symptoms such as; fever, cough, chills, shortness of breath roughly around 4 to 8 hours from exposure to dust, and wheezing.

Pneumonitis symptoms can occur within 4–6 hours after being exposed to inhaling an irritating substance to the lungs.

Symptoms may include: fever, chills, muscle and joint pain, headache, may be mistaken for Flu like symptoms.

Symptoms should go away within a few days, if symptoms worsen you may have developed chronic pneumonitis which includes symptoms such as:

Dry cough, tightness in chest, tiredness/ fatigue, loss of appetite, and weight loss.

## Classification

It can be classified into acute interstitial pneumonitis, blood pneumonitis, lymphocytic interstitial pneumonitis, radiation pneumonitis, and uremic pneumonitis.

Pneumonitis can be separated into several distinct categories based upon causative agent.

Hypersensitivity Pneumonitis (Extrinsic Allergenic Alveolitis) describes the inflammation of alveoli which occurs after inhalation of organic dusts (oxford). These particles can be proteins, bacteria, or mold spores and are usually specific to an occupation.

Acute Interstitial Pneumonitis can result from many different irritants in the lungs and usually is resolved in under a month.

Chemical Pneumonitis is caused by toxic substances reaching the lower airways of the bronchial tree. This causes a chemical burn and severe inflammation. (oxford)

Radiation Pneumonitis, also known as Radiation Induced Lung Injury, describes the initial damage done to the lung tissue by ionization radiation. Radiation, used to treat cancer, can cause pneumonitis when applied to the chest or full body. Radiation pneumonitis occurs in approximately 30% of advanced lung cancer patients treated with radiation therapy.

Aspiration pneumonitis is caused by a chemical inhalation of harmful gastric contents which include causes such as:

* The occurrence in approximately 10% of patients who have been hospitalized due to a drug overdose.
* A lung injury after the inhalation of habitual gestric contents.
* The development of colonized oropharyngeal material after inhalation.
* Bacteria entering the lungs

## Treatment

Typical treatment for pneumonitis includes conservative use of corticosteroids such as a short course of oral prednisone or methylprednisolone. Inhaled corticosteroids such as fluticasone or budesonide may also be effective for reducing inflammation and preventing re-inflammation on a chronic level by suppressing inflammatory processes that may be triggered by environmental exposures such as allergens. Severe cases of pneumonitis may require corticosteroids and oxygen therapy, as well as elimination of exposure to known irritants.

Corticosteroid dose and treatment duration vary from case to case. However, a common regimen beginning at 0.5 mg/kg per day for a couple of days before tapering to a smaller dose for several months to a year, has been used successfully.

Certain immune-modulating treatments may be appropriate for patients suffering from chronic pneumonitis. Azathioprine and mycophenolate are two particular treatments that have been associated with an improvement of gas exchange. Patients with chronic pneumonitis also may be evaluated for lung transplantation.