Most types of eosinophilic pneumonia have similar signs and symptoms. Prominent and nearly universal signs and symptoms include cough, fever, difficulty breathing, and night sweats. Acute eosinophilic pneumonia typically follows a rapid course. Fever and cough may develop only one or two weeks before breathing difficulties progress to the point of respiratory failure requiring mechanical ventilation. Chronic eosinophilic pneumonia usually follows a slower course. Symptoms accumulate over several months and include fever, cough, difficulty breathing, wheezing, and weight loss. Individuals with CEP are often misdiagnosed with asthma before CEP is finally recognized.

EP due to medications or environmental exposures is similar and occurs after an exposure to a known offending agent. EP due to parasitic infections has a similar prodrome in addition to a host of different symptoms related to the variety of underlying parasites. EP in the setting of cancer often develops in the context of a known diagnosis of lung cancer, cervical cancer, etc.

Classification can be complex, and the combined efforts of clinicians, radiologists, and pathologists can help in the generation of a more specific diagnosis.

Idiopathic interstitial pneumonia can be subclassified based on histologic appearance into the following patterns:

Usual interstitial pneumonia is the most common type.

The fibrosing pattern of NSIP has a five year survival rate of 86% to 92%, while the cellular pattern of NSIP has a 100% five year survival rate. Patients with NSIP(whether cellular or fibrosing), have a better prognosis than those with usual interstitial pneumonia (UIP).

Lung biopsies performed on patients with NSIP reveal two different disease patterns - cellular and fibrosing - which are associated with different prognoses. The cellular pattern displays chronic inflammation with minimal fibrosis. The fibrosing pattern displays interstitial fibrosis with various inflammation levels. Both patterns are uniform and lack the prominent fibroblastic foci that are found in other types of idiopathic interstitial pneumonia.

People with infectious pneumonia often have a productive cough, fever accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, and an increased rate of breathing. In the elderly, confusion may be the most prominent sign.

The typical signs and symptoms in children under five are fever, cough, and fast or difficult breathing. Fever is not very specific, as it occurs in many other common illnesses, may be absent in those with severe disease, malnutrition or in the elderly. In addition, a cough is frequently absent in children less than 2 months old. More severe signs and symptoms in children may include blue-tinged skin, unwillingness to drink, convulsions, ongoing vomiting, extremes of temperature, or a decreased level of consciousness.

Bacterial and viral cases of pneumonia usually present with similar symptoms. Some causes are associated with classic, but non-specific, clinical characteristics. Pneumonia caused by "Legionella" may occur with abdominal pain, diarrhea, or confusion, while pneumonia caused by "Streptococcus pneumoniae" is associated with rusty colored sputum, and pneumonia caused by "Klebsiella" may have bloody sputum often described as "currant jelly". Bloody sputum (known as hemoptysis) may also occur with tuberculosis, Gram-negative pneumonia, and lung abscesses as well as more commonly with acute bronchitis. "Mycoplasma" pneumonia may occur in association with swelling of the lymph nodes in the neck, joint pain, or a middle ear infection. Viral pneumonia presents more commonly with wheezing than does bacterial pneumonia. Pneumonia was historically divided into "typical" and "atypical" based on the belief that the presentation predicted the underlying cause. However, evidence has not supported this distinction, thus it is no longer emphasized.

Idiopathic interstitial pneumonia (IIP), or noninfectious pneumonia are a class of diffuse lung diseases. These diseases typically affect the pulmonary interstitium, although some also have a component affecting the airways (for instance, Cryptogenic organizing pneumonitis). There are seven recognized distinct subtypes of IIP.

Usually the atypical causes also involve atypical symptoms:

- No response to common antibiotics such as sulfonamide and beta-lactams like penicillin.

- No signs and symptoms of lobar consolidation, meaning that the infection is restricted to small areas, rather than involving a whole lobe. As the disease progresses, however, the look can tend to lobar pneumonia.

- Absence of leukocytosis.

- Extrapulmonary symptoms, related to the causing organism.

- Moderate amount of sputum, or no sputum at all (i.e. non-productive).

- Lack of alveolar exudate.

- Despite general symptoms and problems with the upper respiratory tract (such as high fever, headache, a dry irritating cough followed later by a productive cough with radiographs showing consolidation), there are in general few physical signs. The patient looks better than the symptoms suggest.

Eosinophilic pneumonia is divided into different categories depending upon whether a cause can be determined or not. Known causes include certain medications or environmental triggers, parasitic infections, and cancer. EP can also occur when the immune system attacks the lungs, a disease called eosinophilic granulomatosis with polyangiitis. When a cause cannot be found, the EP is labeled "idiopathic." Idiopathic EP can be divided into "acute eosinophilic pneumonia" (AEP) and "chronic eosinophilic pneumonia" (CEP) depending on the symptoms a person is experiencing.

The most common symptoms of acute interstitial pneumonitis are highly productive cough with expectoration of thick mucus, fever, and difficulties breathing. These often occur over a period of one to two weeks before medical attention is sought. The presence of fluid means the person experiences a feeling similar to 'drowning'. Difficulties breathing can quickly progress to an inability to breathe without support (respiratory failure).

Acute interstitial pneumonitis typically progresses rapidly, with hospitalization and mechanical ventilation often required only days to weeks after initial symptoms of cough, fever, and difficulties breathing develop.

Acute eosinophilic pneumonia is the acute-onset form of eosinophilic pneumonia, a lung disease caused by the buildup of eosinophils, a type of white blood cell, in the lungs. It is characterized by a rapid onset of shortness of breath, cough, fatigue, night sweats, and weight loss. Though the underlying cause is unknown, it can be triggered by a change in medication or tobacco smoking. It is treated with corticosteroids and has a favorable prognosis.

Signs and symptoms of PCP include fever, non-productive cough (because sputum is too viscous to become productive), shortness of breath (especially on exertion), weight loss, and night sweats. There is usually not a large amount of sputum with PCP unless the patient has an additional bacterial infection. The fungus can invade other visceral organs (such as the liver, spleen, and kidney), but only in a minority of cases.

Pneumothorax is a well-known complication of PCP. An acute history of chest pain with breathlessness and diminished breath sounds is typical of pneumothorax.

Patients with subacute HP gradually develop a productive cough, dyspnea, fatigue, anorexia, weight loss, and pleurisy. Symptoms are similar to the acute form of the disease, but are less severe and last longer. On chest radiographs, micronodular or reticular opacities are most prominent in mid-to-lower lung zones. Findings may be present in patients who have experienced repeated acute attacks.

The subacute, or intermittent, form produces more well-formed noncaseating granulomas, bronchiolitis with or without organizing pneumonia, and interstitial fibrosis.

Alveolar disease is visible on chest radiography as small, ill-defined nodules of homogeneous density centered on the acini or bronchioles. The nodules coalesce early in the course of disease, such that the nodules may only be seen as soft fluffy edges in the periphery.

When the nodules are centered on the hilar regions, the chest x-ray may develop what is called the "butterfly," or "batwing" appearance. The nodules may also have a segmental or lobar distribution. Air alveolograms and air bronchograms can also be seen.

These findings appear soon after the onset of symptoms and change rapidly thereafter.

A segmental or lobar pattern may be apparent after aspiration pneumonia, atelectasis, lung contusion, localized pulmonary edema, obstructive pneumonia, pneumonia, pulmonary embolism with infarction, or tuberculosis.

Desquamative interstitial pneumonia is a form of idiopathic interstitial pneumonia featuring elevated levels of macrophages.

Its name is derived from the former belief that these macrophages were pneumocytes that had desquamated.

It is associated with patients with a history of smoking.

Treatment with methylprednisolone has been reported.

Acute interstitial pneumonitis (also known as acute interstitial pneumonia or Hamman–Rich syndrome) is a rare, severe lung disease that usually affects otherwise healthy individuals. There is no known cause or cure.

Acute interstitial pneumonitis is often categorized as both an interstitial lung disease and a form of acute respiratory distress syndrome (ARDS) but it is distinguished from the "chronic" forms of interstitial pneumonia such as idiopathic pulmonary fibrosis.

The typical symptoms of UIP are progressive shortness of breath and cough for a period of months. In some patients, UIP is diagnosed only when a more acute disease supervenes and brings the patient to medical attention.

In chronic HP, patients often lack a history of acute episodes. They have an insidious onset of cough, progressive dyspnea, fatigue, and weight loss. This is associated with partial to complete but gradual reversibility. Avoiding any further exposure is recommended. Clubbing is observed in 50% of patients. Tachypnea, respiratory distress, and inspiratory crackles over lower lung fields often are present.

On chest radiographs, progressive fibrotic changes with loss of lung volume particularly affect the upper lobes. Nodular or ground-glass opacities are not present. Features of emphysema are found on significant chest films and CT scans.

Chronic forms reveal additional findings of chronic interstitial inflammation and alveolar destruction (honeycombing) associated with dense fibrosis. Cholesterol clefts or asteroid bodies are present within or outside granulomas.

In addition, many patients have hypoxemia at rest, and all patients desaturate with exercise.

Chest radiographs (X-ray photographs) often show a pulmonary infection before physical signs of atypical pneumonia are observable at all.

This is occult pneumonia. In general, occult pneumonia is rather often present in patients with pneumonia and can also be caused by "Streptococcus pneumoniae", as the decrease of occult pneumonia after vaccination of children with a pneumococcal vaccine suggests.

Infiltration commonly begins in the perihilar region (where the bronchus begins) and spreads in a wedge- or fan-shaped fashion toward the periphery of the lung field. The process most often involves the lower lobe, but may affect any lobe or combination of lobes.

The signs and symptoms of PAP include shortness of breath, a cough, low grade fever, and weight loss.

The clinical course of PAP is unpredictable. Spontaneous remission is recognized, and some patients have stable symptoms. Death may occur due to the progression of PAP or of any underlying associated disease. Individuals with PAP are more vulnerable to lung infections such as bacterial pneumonia, mycobacterium avium-intracellulare infection, or a fungal infection.

Alveolar lung disease may be divided into acute or chronic. Causes of acute alveolar lung disease include pulmonary edema (cardiogenic or neurogenic), pneumonia (bacterial or viral), pulmonary embolism, systemic lupus erythematosus, bleeding in the lungs (e.g., Goodpasture syndrome), idiopathic pulmonary hemosiderosis, and granulomatosis with polyangiitis.

Chronic alveolar lung disease can be caused by pulmonary alveolar proteinosis, alveolar cell carcinoma, mineral oil pneumonia, sarcoidosis (alveolar form), lymphoma, tuberculosis, metastases, or desquamative interstitial pneumonia.

Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. Typically symptoms include some combination of productive or dry cough, chest pain, fever, and trouble breathing. Severity is variable.

Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications and conditions such as autoimmune diseases. Risk factors include other lung diseases such as cystic fibrosis, COPD, and asthma, diabetes, heart failure, a history of smoking, a poor ability to cough such as following a stroke, or a weak immune system. Diagnosis is often based on the symptoms and physical examination. Chest X-ray, blood tests, and culture of the sputum may help confirm the diagnosis. The disease may be classified by where it was acquired with community, hospital, or health care associated pneumonia.

Vaccines to prevent certain types of pneumonia are available. Other methods of prevention include handwashing and not smoking. Treatment depends on the underlying cause. Pneumonia believed to be due to bacteria is treated with antibiotics. If the pneumonia is severe, the affected person is generally hospitalized. Oxygen therapy may be used if oxygen levels are low.

Pneumonia affects approximately 450 million people globally (7% of the population) and results in about 4 million deaths per year. Pneumonia was regarded by William Osler in the 19th century as "the captain of the men of death". With the introduction of antibiotics and vaccines in the 20th century, survival improved. Nevertheless, in developing countries, and among the very old, the very young, and the chronically ill, pneumonia remains a leading cause of death. Pneumonia often shortens suffering among those already close to death and has thus been called "the old man's friend".

The cause of the scarring in UIP may be known (less commonly) or unknown (more commonly). Since the medical term for conditions of unknown cause is "idiopathic", the clinical term for UIP of unknown cause is idiopathic pulmonary fibrosis (IPF). Examples of known causes of UIP include systemic sclerosis/scleroderma, rheumatoid arthritis, asbestosis, and prolonged use of medications such as nitrofurantoin or amiodarone.

"Pneumocystis" pneumonia (PCP) is a form of pneumonia, caused by the yeast-like fungus "Pneumocystis jirovecii".

"Pneumocystis" pneumonia is not commonly found in the lungs of healthy people, but, being a source of opportunistic infection, it can cause a lung infection in people with a weak immune system. "Pneumocystis" pneumonia is especially seen in people with cancer undergoing chemotherapy, HIV/AIDS, and the use of medications that suppress the immune system.

Occult pneumonia is a pneumonia that is not observable directly by the eye, but can only be shown indirectly, especially by radiography. Occult pneumonia can be made visible by chest X-rays.

The general symptoms "cough for more than 10 days" and "fever for more than 3 days" can indicate the presence of occult pneumonia, just as a temperature of 39 °C or higher and a high white blood cell count.

Administration of a pneumococcal vaccine decreases the incidence of occult pneumonia, which suggests that "Streptococcus pneumoniae" is a cause of occult pneumonia. Occult pneumonia, however, can also be the result of atypical pneumonia.

Although pneumococcal vaccination lowers the prevalence of occult pneumonia, it does not make radiographic diagnosis superfluous at patients with prolonged fever, cough or leukocytosis.

Etymology: the term is derived from the Latin "occultus" = hidden, secret and "pneumonia" = inflammation of the lungs > Greek: "pneuma" = wind and Indo-European: "pleumon" = floating, swimming.

Pneumonia is an illness which can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites. Pneumonia can occur in any animal with lungs, including mammals, birds, and reptiles.

Symptoms associated with pneumonia include fever, fast or difficult breathing, nasal discharge, and decreased activity.

Different animal species have distinct lung anatomy and physiology and are thus

affected by pneumonia differently. Differences in anatomy, immune systems, diet, and behavior also affects the particular microorganisms commonly causing

pneumonia. Diagnostic tools include physical examination, testing of the

sputum, and x-ray investigation. Treatment depends on the cause of pneumonia;

bacterial pneumonia is treated with antibiotics.

"See also:" Pneumonia, Pneumonic.