The prognosis of nocardiosis is highly variable. The state of the host's health, site, duration, and severity of the infection all play parts in determining the prognosis. As of now, skin and soft tissue infections have a 100% cure rate, and pleuropulmonary infections have a 90% cure rate with appropriate therapy. The cure rate falls to 63% with those infected with dissemented nocardiosis, with only half of those surviving infections that cause brain abscess. Additionally, 44% of people who are infected in the spinal cord/brain die, increasing to 85% if that person has an already weakened immune system. Unfortunately, there is not a preventative to nocardiosis. The only recommendation is to protect open wounds to limit access.

Although there is not international data available on worldwide infection rates per year, there are roughly 500–1000 documented cases of nocardiosis a year. Most of these cases occur in men, as there is a 3:1 ratio of male of female cases a year; however, this difference may be based on exposure frequency rather than susceptibility differences. From an age perspective, it is not highly more prevalent in one age group than another. Cutaneous Nocardiosis is slightly more common in middle aged men, but as a whole, all ages are susceptible. Additionally, there is no racial basis when it comes to becoming infected with Nocardiosis.

Medications, substance abuse, and environmental exposures may all trigger eosinophil dysfunction. Medications such as NSAIDs (e.g. ibuprofen), nitrofurantoin, phenytoin, L-tryptophan, daptomycin and ampicillin and drugs of abuse such as inhaled heroin and cocaine may trigger an allergic response which results in EP. Chemicals such as sulfites, aluminum silicate, and cigarette smoke can cause EP when inhaled. A New York City firefighter developed EP after inhalation of dust from the World Trade Center on September 11, 2001.

Eosinophilic pneumonia can develop in several different ways depending on the underlying cause of the disease. Eosinophils play a central role in defending the body against infection by parasites. Many diseases, such as asthma and eczema, are caused when eosinophils overreact to environmental triggers and release an excess of chemicals, e.g. cytokines and histamine. The common characteristic among different causes of EP is eosinophil overreaction or dysfunction in the lung.

According to a recent study, the main risk factors for RA-ILD are advancing age, male sex, greater RA disease activity, rheumatoid factor (RF) positivity, and elevated titers of anticitrullinated protein antibodies such as anticyclic citrullinated peptide. Cigarette smoking also appears to increase risk of RA-ILD, especially in patients with human leukocyte antigen DRB1.

A recently published retrospective study by a team from Beijing Chao-Yang Hospital in Beijing, China, supported three of the risk factors listed for RA-ILD and identified an additional risk factor. In that study of 550 RA patients, logistic regression analysis of data collected on the 237 (43%) with ILD revealed that age, smoking, RF positivity, and elevated lactate dehydrogenase closely correlated with ILD.

Recent studies have identified risk factors for disease progression and mortality. A retrospective study of 167 patients with RA-ILD determined that the usual interstitial pneumonia (UIP) pattern on high-resolution computed tomography (HRCT) was a risk factor for progression, as were severe disease upon diagnosis and rate of change in pulmonary function test results in the first 6 months after diagnosis.

A study of 59 RA-ILD patients found no median survival difference between those with the UIP pattern and those without it. But the UIP group had more deaths, hospital admissions, need for supplemental oxygen, and decline in lung function.

The most common organ affected by aspergilloma is the lung. Aspergilloma mainly affects people with underlying cavitary lung disease such as tuberculosis, sarcoidosis, bronchiectasis, cystic fibrosis and systemic immunodeficiency. "Aspergillus fumigatus", the most common causative species, is typically inhaled as small (2 to 3 micron) spores. The fungus settles in a cavity and is able to grow free from interference because critical elements of the immune system are unable to penetrate into the cavity. As the fungus multiplies, it forms a ball, which incorporates dead tissue from the surrounding lung, mucus, and other debris.

In the post-antibiotic era pattern of frequency is changing. In older studies anaerobes were found in up to 90% cases but they are much less frequent now.

Most cases respond to antibiotics and prognosis is usually excellent unless there is a debilitating underlying condition. Mortality from lung abscess alone is around 5% and is improving.

Most cases of aspergilloma do not require treatment. Treatment of diseases which increase the risk of aspergilloma, such as tuberculosis, may help to prevent their formation. In cases complicated by severe hemoptysis or other associated conditions such as pleural empyema or pneumothorax, surgery may be required to remove the aspergilloma and the surrounding lung tissue by doing a lobectomy or other types of resection and thus stop the bleeding. There has been interest in treatment with antifungal medications such as itraconazole, none has yet been shown to reliably eradicate aspergillomata.

Although most fungi — especially "Aspergillus" — fail to grow in healthy human tissue, significant growth may occur in people whose adaptive immune system is compromised, such as those with chronic granulomatous disease, who are undergoing chemotherapy, or who have recently undergone a bone marrow transplantation. Within the lungs of such individuals, the fungal hyphae spread out as a spherical growth. With the restoration of normal defense mechanisms, neutrophils and lymphocytes are attracted to the edge of the spherical fungal growth where they lyse, releasing tissue-digesting enzymes as a normal function. A sphere of the infected lung is thus cleaved from the adjacent lung. This sphere flops around in the resulting cavity and is recognized on x-ray as a fungus ball. This process is beneficial as a potentially serious invasive fungal infection is converted into surface colonization. Although the fungus is inactivated in the process, surgeons may choose to operate to reduce the possibility of bleeding. Microscopic examination of surgically removed recently formed fungus balls clearly shows a sphere of dead lung containing fungal hyphae. Microscopic examination of older lesions reveals mummified tissue which may reveal faint residual lung or hyphal structures.

BFL symptoms improve in the absence of the bird proteins which caused the disease. Therefore, it is advisable to remove all birds, bedding and pillows containing feathers from the house as well as washing all soft furnishings, walls, ceilings and furniture. Certain small mammals kept as pets have the same or similar proteins in their fur and feces and so should be removed. Peak flow measurements will indicate a lung condition however a spirometric test on lung capacity and patients ability to move air in and out of the lungs plus in more advanced cases an X-ray test or CT scan is available to confirm whether someone has the disease or not. Steroid inhalers similar to those used for asthma are effective or in cases where the patient finds inhaling difficult high dosages of steroids combined with bone density protecting drugs are used to treat a person with BFL, reducing the inflammation and hopefully preventing scarring. Recovery varies from patient to patient depending on what stage the condition was at when the patient consulted the doctor, the speed of diagnosis and application of the appropriate treatment to prevent residual damage to the lungs and many make a full recovery. However, BFL may reoccur when in contact with birds or other allergens.

OPA has been found in most countries where sheep are farmed, with the exception of Australia and New Zealand. OPA has been eradicated in Iceland.

No breed or sex of sheep appears to be predisposed to OPA. Most affected sheep show signs at 2 to 4 years of age.

OPA is not a notifiable disease, and therefore it is difficult to assess its prevalence.

ILD may be classified according to the cause. One method of classification is as follows:

1. Inhaled substances

- Inorganic

- Silicosis

- Asbestosis

- Berylliosis

- printing workers (eg. carbon bblack, ink mist)

- Organic

- Hypersensitivity pneumonitis

2. Drug-induced

- Antibiotics

- Chemotherapeutic drugs

- Antiarrhythmic agents

3. Connective tissue and Autoimmune diseases

- Rheumatoid arthritis

- Systemic lupus erythematosus

- Systemic sclerosis

- Polymyositis

- Dermatomyositis

4. Infection

- Atypical pneumonia

- Pneumocystis pneumonia (PCP)

- Tuberculosis

- "Chlamydia" trachomatis

- Respiratory Syncytial Virus

5. Idiopathic

- Sarcoidosis

- Idiopathic pulmonary fibrosis

- Hamman-Rich syndrome

- Antisynthetase syndrome

6. Malignancy

- Lymphangitic carcinomatosis

7. Predominantly in children

- Diffuse developmental disorders

- Growth abnormalities deficient alveolarisation

- Infant conditions of undefined cause

- ILD related to alveolar surfactant region

Transient tachypnea of the newborn occurs in approximately 1 in 100 preterm infants and 3.6-5.7 per 1000 term infants. It is most common in infants born by Cesarian section without a trial of labor after 35 weeks' gestation. Male infants and infants with an umbilical cord prolapse or perinatal asphyxia are at higher risk. Parental risk factors include use of pain control or anesthesia during labor, asthma, and diabetes.

Respiratory disease is a common and significant cause of illness and death around the world. In the US, approximately 1 billion "common colds" occur each year. A study found that in 2010, there were approximately 6.8 million emergency department visits for respiratory disorders in the U.S. for patients under the age of 18. In 2012, respiratory conditions were the most frequent reasons for hospital stays among children.

In the UK, approximately 1 in 7 individuals are affected by some form of chronic lung disease, most commonly chronic obstructive pulmonary disease, which includes asthma, chronic bronchitis and emphysema.

Respiratory diseases (including lung cancer) are responsible for over 10% of hospitalizations and over 16% of deaths in Canada.

In 2011, respiratory disease with ventilator support accounted for 93.3% of ICU utilization in the United States.

Regardless of cause, UIP is relentlessly progressive, usually leading to respiratory failure and death without a lung transplant. Some patients do well for a prolonged period of time, but then deteriorate rapidly because of a superimposed acute illness (so-called "accelerated UIP"). The outlook for long-term survival is poor. In most studies, the median survival is 3 to 4 years. Patients with UIP in the setting of rheumatoid arthritis have a slightly better prognosis than UIP without a known cause (IPF).

Hypersensitivity pneumonitis may also be called many different names, based on the provoking antigen. These include:

Of these types, Farmer's Lung and Bird-Breeder's Lung are the most common. "Studies document 8-540 cases per 100,000 persons per year for farmers and 6000-21,000 cases per 100,000 persons per year for pigeon breeders. High attack rates are documented in sporadic outbreaks. Prevalence varies by region, climate, and farming practices. HP affects 0.4–7% of the farming population. Reported prevalence among bird fanciers is estimated to be 20-20,000 cases per 100,000 persons at risk."

Bird fancier's lung is a type of hypersensitivity pneumonitis caused by bird droppings. The lungs become inflamed with granuloma formation.

Bird fancier's lung (BFL), also called "bird-breeder's lung" and "pigeon-breeder's lung", is a subset of hypersensitivity pneumonitis (HP). This disease is caused by the exposure to avian proteins present in the dry dust of the droppings and sometimes in the feathers of a variety of birds. Birds such as pigeons, parakeets, cockatiels, shell parakeets (budgerigars), parrots, turtle doves, turkeys and chickens have been implicated.

People who work with birds or own many birds are at risk. Bird hobbyists and pet store workers may also be at risk.

Why only some people with CVID are affected by GLILD remains unknown. However, there have been reports that elevated levels of IgM antibodies, altered T-cell function and/or proportionality of CD4:CD8 T cells may be associated with increased risk of GLILD, and GLILD has also been associated with specific genetic mutations in CVID, including CTLA-4 deficiency.

The exact cause of rheumatoid lung disease is unknown. However, associated factors could be due largely to smoking. Sometimes, the medicines used to treat rheumatoid arthritis, especially methotrexate, may result in lung disease.

Prevention's:

- Stop smoking: Chemicals found in cigarettes can irritate already delicate lung tissue, leading to further complications.

- Having regular checkups: The doctor could listen to lungs and monitor breathing, because lung problems that are detected early can be easier to treat.

VALI is most common in patients receiving mechanical ventilation for acute lung injury or acute respiratory distress syndrome (ALI/ARDS).

Possible reasons for predisposition to VALI include:

- An injured lung may be at risk for further injury

- Cyclic atelectasis is particularly common in an injured lung

Conditions which commonly involve hemoptysis include bronchitis and pneumonia, lung cancers and tuberculosis. Other possible underlying causes include aspergilloma, bronchiectasis, coccidioidomycosis, pulmonary embolism, pneumonic plague, and cystic fibrosis. Rarer causes include hereditary hemorrhagic telangiectasia (HHT or Rendu-Osler-Weber syndrome), Goodpasture's syndrome, and granulomatosis with polyangiitis. In children, hemoptysis is commonly caused by the presence of a foreign body in the airway. The condition can also result from over-anticoagulation from treatment by drugs such as warfarin.

Blood-laced mucus from the sinus or nose area can sometimes be misidentified as symptomatic of hemoptysis (such secretions can be a sign of nasal or sinus cancer, but also a sinus infection). Extensive non-respiratory injury can also cause one to cough up blood. Cardiac causes like congestive heart failure and mitral stenosis should be ruled out.

The origin of blood can be identified by observing its color. Bright-red, foamy blood comes from the respiratory tract, whereas dark-red, coffee-colored blood comes from the gastrointestinal tract. Sometimes hemoptysis may be rust-colored.

The most common cause of minor hemoptysis is bronchitis.

- Lung cancer, including both non-small cell lung carcinoma and small cell lung carcinoma.

- Sarcoidosis

- Aspergilloma

- Tuberculosis

- Histoplasmosis

- Pneumonia

- Pulmonary edema

- Pulmonary embolism

- Foreign body aspiration and aspiration pneumonia

- Goodpasture's syndrome

- Granulomatosis with polyangiitis

- Eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome)

- Bronchitis

- Bronchiectasis

- Pulmonary embolism

- Anticoagulant use

- Trauma

- Lung abscess

- Mitral stenosis

- Tropical eosinophilia

- Bleeding disorders

- Hughes-Stovin Syndrome and other variants of Behçet's disease

- Squamous Cell Carcinoma Of Esophagus

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.

The Great Imitator (also The Great Masquerader) is a phrase used for medical conditions that feature nonspecific symptoms and may be confused with a number of other diseases. Most great imitators are systemic in nature. Diseases sometimes referred to with this name include:

- Various cancers

- Intravascular large B-cell lymphoma

- Various rheumatic conditions, including:

- Fibromyalgia

- Psoriatic arthritis

- Lupus erythematosus

- Systemic lupus erythematosus

- Sarcoidosis

- Multiple sclerosis

- Celiac disease

- Addison's Disease

- Pulmonary embolism

- Various infectious diseases, including:

- Syphilis

- Lyme disease

- Nocardiosis

- Tuberculosis

- Brucellosis

- Malaria

- Breathing-related sleep disorders (chiefly sleep apnea/hypopnea and upper-airway resistance syndrome).

PAP patients, families, and caregivers are encouraged to join the NIH Rare Lung Diseases Consortium Contact Registry. This is a privacy protected site that provides up-to-date information for individuals interested in the latest scientific news, trials, and treatments related to rare lung diseases.

The disease is more common in males and in tobacco smokers.

In a recent epidemiologic study from Japan, Autoimmune PAP has an incidence and prevalence higher than previously reported and is not strongly linked to smoking, occupational exposure, or other illnesses.

Endogenous lipoid pneumonia and non-specific interstitial pneumonitis has been seen prior to the development of PAP in a child.