The morbidity associated with DIPNECH is due to the associated obstructive lung disease. The lung disease tends to be slowly progressive, but given enough time can lead to significant disability and require supplemental oxygen therapy. There have been reports of lung transplantation in the setting of end-stage DIPNECH.

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.

To date there have been no clinical trials to determine effective treatment for this disease. Some patients have been treated with somatostatin analogs. Although the cough associated with DIPNECH tends to diminish on this treatment, improvement in pulmonary function has not been clearly demonstrated. There are also reports of symptomatic treatment with long- and short-acting beta agonists. Although steroids, both oral and inhaled, have been used in the setting of DIPNECH, there is no clear improvement with this treatment.

It is not uncommon for typical carcinoids to arise within DIPNECH. Due to presence of these tumors, DIPNECH is classified as a pre-malignant condition. Although there have been reports of atypical carcinoids with local lymph node involvement, there are no reports of more aggressive neuroendocrine tumors, such as large cell neuroendocrine or small cell lung cancer, associated with DIPNECH. When isolated bronchial carcinoids are diagnosed, oncology guidelines recommend surgical resection with lymph node sampling. However, as multiple carcinoids may develop in the setting of DIPNECH, a more conservative approach is often considered to preserve lung function.

Multifocal micronodular pneumocyte hyperplasia (MMPH) is a subtype of pneumocytic hyperplasia (hyperplasia of pneumocytes lining pulmonary alveoli).

Several synonymous terms have been done for this entity: adenomatoid proliferation of alveolar epithelium, papillary alveolar hamartoma, multifocal alveolar hyperplasia, multinodular pneumocyte hyperplasia.

These multifocal lesions are observed in tuberous sclerosis, and can be associated with lymphangioleiomyomatosis and perivascular epithelioid cell tumour (PEComa or clear cell "sugar tumor")).

It can be diagnosed through lung biopsy using thoracoscopy.

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

Pulmonary fibrosis may be a secondary effect of other diseases. Most of these are classified as interstitial lung diseases. Examples include autoimmune disorders, viral infections and bacterial infection like tuberculosis which may cause fibrotic changes in both lungs upper or lower lobes and other microscopic injuries to the lung. However, pulmonary fibrosis can also appear without any known cause. In this case, it is termed "idiopathic". Most idiopathic cases are diagnosed as "idiopathic pulmonary fibrosis". This is a diagnosis of exclusion of a characteristic set of histologic/pathologic features known as usual interstitial pneumonia (UIP). In either case, there is a growing body of evidence which points to a genetic predisposition in a subset of patients. For example, a mutation in surfactant protein C (SP-C) has been found to exist in some families with a history of pulmonary fibrosis.

Diseases and conditions that may cause pulmonary fibrosis as a secondary effect include:

- Inhalation of environmental and occupational pollutants, such as metals in asbestosis, silicosis and exposure to certain gases. Coal miners, ship workers and sand blasters among others are at higher risk.

- Hypersensitivity pneumonitis, most often resulting from inhaling dust contaminated with bacterial, fungal, or animal products.

- Cigarette smoking can increase the risk or make the illness worse.

- Some typical connective tissue diseases such as rheumatoid arthritis, SLE and scleroderma

- Other diseases that involve connective tissue, such as sarcoidosis and granulomatosis with polyangiitis.

- Infections

- Certain medications, e.g. amiodarone, bleomycin (pingyangmycin), busulfan, methotrexate, apomorphine, and nitrofurantoin

- Radiation therapy to the chest

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.

Tobacco smoking is by far the main contributor to lung cancer. Cigarette smoke contains at least 73 known carcinogens, including benzo["a"]pyrene, NNK, 1,3-butadiene and a radioactive isotope of polonium, polonium-210. Across the developed world, 90% of lung cancer deaths in men during the year 2000 were attributed to smoking (70% for women). Smoking accounts for about 85% of lung cancer cases.

Passive smoking—the inhalation of smoke from another's smoking—is a cause of lung cancer in nonsmokers. A passive smoker can be defined as someone living or working with a smoker. Studies from the US, Europe and the UK have consistently shown a significantly increased risk among those exposed to passive smoke. Those who live with someone who smokes have a 20–30% increase in risk while those who work in an environment with secondhand smoke have a 16–19% increase in risk. Investigations of sidestream smoke suggest it is more dangerous than direct smoke. Passive smoking causes about 3,400 deaths from lung cancer each year in the USA.

Marijuana smoke contains many of the same carcinogens as those in tobacco smoke. However, the effect of smoking cannabis on lung cancer risk is not clear. A 2013 review did not find an increased risk from light to moderate use. A 2014 review found that smoking cannabis doubled the risk of lung cancer.

Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of lung diseases affecting the interstitium (the tissue and space around the air sacs of the lungs). It concerns alveolar epithelium, pulmonary capillary endothelium, basement membrane, perivascular and perilymphatic tissues. It may occur when an injury to the lungs triggers an abnormal healing response. Ordinarily, the body generates just the right amount of tissue to repair damage. But in interstitial lung disease, the repair process goes awry and the tissue around the air sacs (alveoli) becomes scarred and thickened. This makes it more difficult for oxygen to pass into the bloodstream. The term ILD is used to distinguish these diseases from obstructive airways diseases.

In children, several unique forms of ILD exist which are specific for the young age groups. The acronym chILD is used for this group of diseases and is derived from the English name, Children’s Interstitial Lung Diseases – chILD.

Prolonged ILD may result in pulmonary fibrosis, but this is not always the case. Idiopathic pulmonary fibrosis is interstitial lung disease for which no obvious cause can be identified (idiopathic), and is associated with typical findings both radiographic (basal and pleural based fibrosis with honeycombing) and pathologic (temporally and spatially heterogeneous fibrosis, histopathologic honeycombing and fibroblastic foci).

In 2013 interstitial lung disease affected 595,000 people globally. This resulted in 471,000 deaths.

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.

Five million people worldwide are affected by pulmonary fibrosis. A wide range of incidence and prevalence rates have been reported for pulmonary fibrosis. The rates below are per 100,000 persons, and the ranges reflect narrow and broad inclusion criteria, respectively.

Based on these rates, pulmonary fibrosis prevalence in the United States could range from more than 29,000 to almost 132,000, based on the population in 2000 that was 18 years or older. The actual numbers may be significantly higher due to misdiagnosis. Typically, patients are in their forties and fifties when diagnosed while the incidence of idiopathic pulmonary fibrosis increases dramatically after the age of fifty. However, loss of pulmonary function is commonly ascribed to old age, heart disease or to more common lung diseases.

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.

Typical pulmonary carcinoid tumour is a subtype of pulmonary carcinoid tumour. It is an uncommon low-grade malignant lung mass that is most often in the central airways of the lung.

It is also known as typical lung carcinoid tumour, lung carcinoid, and typical lung carcinoid.

There is very little information written by, and for patients with GLILD. However, interest in the condition is increasing and multi-centre studies such as STILPAD are in progress.

Pulmonary diseases may also impact newborns, such as pulmonary hyperplasia, pulmonary interstitial emphysema (usually preterm births), and infant respiratory distress syndrome,

Many cases of restrictive lung disease are idiopathic (have no known cause). Still, there is generally pulmonary fibrosis. Examples are:

- Idiopathic pulmonary fibrosis

- Idiopathic interstitial pneumonia, of which there are several types

- Sarcoidosis

- Eosinophilic pneumonia

- Lymphangioleiomyomatosis

- Pulmonary Langerhans' cell histiocytosis

- Pulmonary alveolar proteinosis

Conditions specifically affecting the interstitium are called interstitial lung diseases.

Restrictive lung diseases may be due to specific causes which can be intrinsic to the parenchyma of the lung, or extrinsic to it.

Folliculosebaceous cystic hamartoma abbreviated as (FSCH) is a rare cutaneous hamartoma consisting of dilated folliculosebaceous units invested in mesenchymal elements. it typically affects adults, have a predilection for the central face or scalp, with less than 1.5 cm dimension. Clinically, the lesions are asymptomatic, rubbery to firm in consistency, and usually occur on or above the neck in (> 90%) of cases, Histopathologically, FSCH shares several similar features to sebaceous trichofolliculoma, but it is usually possible to differentiate these two tumors.

Outdoor air pollutants, especially chemicals released from the burning of fossil fuels, increase the risk of lung cancer. Fine particulates (PM) and sulfate aerosols, which may be released in traffic exhaust fumes, are associated with slightly increased risk. For nitrogen dioxide, an incremental increase of 10 parts per billion increases the risk of lung cancer by 14%. Outdoor air pollution is estimated to account for 1–2% of lung cancers.

Tentative evidence supports an increased risk of lung cancer from indoor air pollution related to the burning of wood, charcoal, dung or crop residue for cooking and heating. Women who are exposed to indoor coal smoke have about twice the risk and a number of the by-products of burning biomass are known or suspected carcinogens. This risk affects about 2.4 billion people globally, and is believed to account for 1.5% of lung cancer deaths.

The National Institute of Occupational Safety and Health, Japan (JNIOSH) set limits for acceptable exposure at 0.0003 mg/m after the discovery of indium lung. Methods for reducing indium exposure are thought to be the best mode of protection. Medical surveillance of indium workers is also a method of prevention.

Lung carcinoids typically present with a cough or hemoptysis. Findings may closely mimic malignant tumours of the lung, i.e. lung cancer.

Fibrous hamartoma of infancy is a rapidly growing, painless, ill-defined subcutaneous or intradermal nodule that is generally solitary and less than 5 cm in size, though, rarely, multiple lesions occur synchronously.

By 1999, there were 12 reported cases.

The majority of patients are less than 2 years old, with 25% of cases being congenital. Possible locations include the trunk and limbs; usually the upper arm or shoulder. Local excision is the treatment of choice, but it may recur locally.

A basaloid follicular hamartoma is a cutaneous condition characterized as distinctive benign adnexal tumor that has several described variants.

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

A bile duct hamartoma or biliary hamartoma, is a benign tumour-like malformation

of the liver.

They are classically associated with polycystic liver disease, as may be seen in the context of polycystic kidney disease, and represent a malformation of the liver plate.