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 diagnoses 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. Classification 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: Aspiration due to a drug overdose A lung injury after the inhalation of habitual gastric 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