Pneumonia overview

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Editor(s)-in-Chief: C. Michael Gibson, M.S., M.D. [1] Phone:617-632-7753; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2]

Overview

Pneumonia is an illness of the lungs and respiratory system in which the alveoli (microscopic air-filled sacs of the lung responsible for absorbing oxygen from the atmosphere become inflamed and flooded with fluid. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing.Diagnostic tools include x-rays and examination of the sputum. Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics. Pneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically and terminally ill. Vaccines to prevent certain types of pneumonia are available. The prognosis depends on the type of pneumonia, the appropriate treatment, any complications, and the person's underlying health.

Community-acquired pneumonia

Community-acquired pneumonia (CAP), also known as walking pneumonia, is a disease in which individuals who have not recently been hospitalized develop an infection of the lungs. CAP is a common illness and can affect people of all ages. It often causes problems like breathing, fever, chest pains, and a cough. CAP occurs when (alveoli) become filled with fluid and cannot work effectively. It occurs throughout the world and is a leading cause of illness and death. Causes of CAP include bacteria, viruses, fungi, and parasites. CAP can be diagnosed by symptoms and physical examination alone, though x-rays, examination of the sputum, and other tests are often used. CAP is primarily treated with antibiotic medication. Some forms of CAP can be prevented by vaccination.

Viral pneumonia

Viral pneumonia is an inflammation of the lung caused by a virus. Viruses are the most common cause of pneumonia in children. Viral pneumonia is commonly caused by viruses such as influenza virus, respiratory syncytial virus (RSV), adenovirus, and metapneumovirus.Herpes simplex virus is a rare cause of pneumonia except in newborns. People with immune system problems are also at risk of pneumonia caused bycytomegalovirus (CMV).

Fungal pneumonia

Fungal pneumonia is an infection of the lungs by fungi. It can be caused by either endemic or opportunistic fungi or a combination of both.Fungal pneumonia is uncommon, but it may occur in individuals with immune system problems due to AIDS, immunosuppresive drugs, or other medical problems. The pathophysiology of pneumonia caused by fungi is similar to that of bacterial pneumonia. Fungal pneumonia is most often caused byHistoplasma capsulatum, Cryptococcus neoformans, Pneumocystis jiroveci, and Coccidioides immitis.Histoplasmosis is most common in the Mississippi River basin, and coccidioidomycosis in the southwestern United States.

Aspiration pneumonia

Aspiration pneumonia (or aspiration pneumonitis) is caused by aspirating foreign objects which are usually oral or gastric contents, either while eating, or after reflux or vomiting which results in bronchopneumonia. The resulting lung inflammation is not an infection but can contribute to one, since the material aspirated may contain anaerobic bacteria or other unusual causes of pneumonia. Aspiration is a leading cause of death among hospital and nursing home patients, since they often cannot adequately protect their airways and may have otherwise impaired defenses.

Parasitic pneumonia

A variety of parasites can affect the lungs. It is a rare cause of pneumonia, occurring almost exclusively in immunocompromised persons, such as persons suffering from AIDS. This is a Respiratory infection that may or may not be serious. There are a variety of parasites which can affect the lungs. In general, these parasites enter the body through the skin or by being swallowed. Once inside the body, these parasites travel to the lungs, most often through the blood. There, a similar combination of cellular destruction and immune response causes disruption of oxygen transportation. One type of white blood cell, the eosinophil, responds vigorously to parasite infection. Eosinophils in the lungs can lead toeosinophilic pneumonia, thus complicating the underlying parasitic pneumonia. The most common parasites involved: Toxoplasma gondii, Strongyloides stercoralis,Ascariasis, Hookworm