Pneumonitis describes general inflammation of lung tissue. Possible causative agents include radiation therapy of the chest, exposure to medications used during chemo-therapy, the inhalation of debris (e.g., animal dander), aspiration, herbicides or fluorocarbons and some systemic diseases. If unresolved, continued inflammation can result in irreparable damage such as pulmonary fibrosis. Pneumonitis is distinguished from pneumonia on the basis of causation as well as its manifestation. Pneumonia can be described as pneumonitis combined with consolidation and exudation of lung tissue due to infection with microorganisms. The distinction between pneumonia and pneumonitis can be further understood with pneumonitis being the encapsulation of all respiratory infections (incorporating pneumonia and pulmonary fibrosis as major diseases), and pneumonia as a localized infection. For most infections, the immune response of the body 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. Pneumonitis can be classified into several different specific subcategories, including hypersensitivity pneumonitis, radiation pneumonitis, acute interstitial pneumonitis, and chemical pneumonitis. These all share similar symptoms, but differ in causative agents. Diagnosis of pneumonitis remains challenging, but several different treatment paths (corticosteroids, oxygen therapy, avoidance) have seen success.
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. Cytomegalovirus (CMV) is another cause. Pneumonia Radiation therapy Immunotherapy 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 "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 Whole body or chest radiation therapy used for cancer treatment
Symptoms Physical manifestations of Pneumonitis range from mild cold-like symptoms to respiratory failure. Most frequently, those with pneumonitis experience shortness of breath, and sometimes a dry cough. Symptoms usually appear a few hours after exposure and peak at approximately eighteen to twenty-four hours. Other symptoms may include:
Malaise Fever Dyspnea Flushed and/or discolored skin Sweating Small and fast inhalations Without proper treatment, pneumonitis may become chronic pneumonitis, resulting in fibrosis of the lungs and its effects:
Difficulty breathing Food aversion Lethargy End-stage fibrosis and respiratory failure eventually lead to death in cases without proper management of chronic pneumonitis.
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:
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