Usual interstitial pneumonia (UIP) is a form of

lung disease The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side ...

characterized by progressive scarring of both lungs. The scarring (

fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...

) involves the pulmonary interstitium (the supporting framework of the lung). UIP is thus classified as a form of

interstitial lung disease Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium (the tissue and space around the alveoli (air sacs)) of the lungs. It concerns alveolar epithelium, pu ...

Terminology

The term "usual" refers to the fact that UIP is the most common form of interstitial fibrosis. "Pneumonia" indicates "lung abnormality", which includes fibrosis and inflammation. A term previously used for UIP in the British literature is cryptogenic fibrosing alveolitis (CFA), a term that has fallen out of favor since the basic underlying pathology is now thought to be fibrosis, not inflammation. The term usual interstitial pneumonitis (UIP) has also often been used, but again, the ''-itis'' part of that name may overemphasize inflammation.

Signs and symptoms

The typical symptoms of UIP are progressive

shortness of breath Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing di ...

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.

Causes

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 Idiopathic pulmonary fibrosis (IPF), or (formerly) fibrosing alveolitis, is a rare, progressive illness of the respiratory system, characterized by the thickening and stiffening of lung tissue, associated with the formation of scar tissue. It is ...

(IPF). Examples of known causes of UIP include

connective tissue disease A connective tissue disease (collagenosis) is any disease that has the connective tissues of the body as a target of pathology. Connective tissue is any type of biological tissue with an extensive extracellular matrix that supports, binds togeth ...

s (primarily

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and hands are invol ...

), drug toxicity, chronic

hypersensitivity pneumonitis Hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis (EAA) is a syndrome caused by the repetitive inhalation of antigens from the environment in susceptible or sensitized people. Common antigens include molds, bacteria, bird dropping ...

asbestosis Asbestosis is long-term inflammation and scarring of the lungs due to asbestos fibers. Symptoms may include shortness of breath, cough, wheezing, and chest tightness. Complications may include lung cancer, mesothelioma, and pulmonary heart d ...

and

Hermansky–Pudlak syndrome Heřmanský–Pudlák syndrome (often written Hermansky–Pudlak syndrome or abbreviated HPS) is an extremely rare autosomal recessive disorder which results in oculocutaneous albinism (decreased pigmentation), bleeding problems due to a platele ...

Diagnosis

UIP (Usual interstitial pneumonia)-CT scan

UIP may be diagnosed by a radiologist using computed tomography (CT) scan of the chest, or by a pathologist using tissue obtained by a lung biopsy.

Radiology

Radiologically, the main feature required for a confident diagnosis of UIP is honeycomb change in the periphery and the lower portions (bases) of the lungs. On

high-resolution computed tomography High-resolution computed tomography (HRCT) is a type of computed tomography (CT) with specific techniques to enhance image resolution. It is used in the diagnosis of various health problems, though most commonly for lung disease, by assessing t ...

(HRCT), the following categories, depending on imaging findings, have been recommended by a collaborative effort by the

American Thoracic Society The American Thoracic Society (ATS) is a nonprofit organization focused on improving care for pulmonary diseases, critical illnesses and sleep-related breathing disorders. It was established in 1905 as the American Sanatorium Association, and ...

European Respiratory Society The European Respiratory Society, or ERS, is a non-profit organization with offices in Lausanne, Brussels and Sheffield. It was founded in 1990 in the field of respiratory medicine. The organization was formed with the merger of the Societas Euro ...

, Japanese Respiratory Society, and the Latin American Thoracic Society: *UIP pattern: :*

Honeycombing Honeycombing or "honeycomb lung" is the radiological appearance seen with widespread fibrosis and is defined by the presence of small cystic spaces with irregularly thickened walls composed of fibrous tissue Fiber or fibre (from la, fibr ...

, with or without peripheral traction bronchiectasis; or bronchiolectasis (dilatation of the terminal bronchioles) :*Predominantly subpleural and basal :*Often heterogenous distribution, being occasionally diffuse, and may be asymmetrical There may be superimposed CT features such as mild

ground-glass opacity Ground-glass opacity (GGO) is a finding seen on chest x-ray (radiograph) or computed tomography (CT) imaging of the lungs. It is typically defined as an area of hazy opacification (x-ray) or increased attenuation (CT) due to air displacement by ...

, reticular pattern and pulmonary ossification. *Probable UIP pattern: :*Predominantly subpleural and basal :*Often heterogenous distribution :*Reticular pattern with peripheral traction bronchiectasis or bronchiolectasis :*There may be mild ground-glass opacity *Indeterminate for UIP: :*Predominantly subpleural and basal :*Subtle reticular pattern :*May have mild ground-glass opacity or distortion (“early UIP pattern”) *Findings suggestive of another diagnosis, including: :*Other predominant distribution: ::*Peribronchovascular ::*Perilymphatic ::*Upper or mid-lung :*Cysts :*Marked mosaic pattern :*Predominant ground-glass opacity :*Profuse lung micronodules :*

Lung nodule A lung nodule or pulmonary nodule is a relatively small focal density in the lung. A solitary pulmonary nodule (SPN) or coin lesion, is a mass in the lung smaller than three centimeters in diameter. A pulmonary micronodule has a diameter of less ...

s, especially centrilobular :*Consolidation :*

Pleural plaques Pleural thickening is an increase in the bulkiness of one or both of the pulmonary pleurae. Causes Pleural plaques Pleural plaques are patchy collections of hyalinized collagen in the parietal pleura. They have a holly leaf appearance on X-ray. ...

(indicating asbestosis) :*Dilated esophagus (indicating

) :*Distal clavicular erosions (indicating

) :*Extensive lymph node enlargement :*

Pleural effusion A pleural effusion is accumulation of excessive fluid in the pleural space, the potential space that surrounds each lung. Under normal conditions, pleural fluid is secreted by the parietal pleural capillaries at a rate of 0.6 millilitre per k ...

:*Pleural thickening (indicating

/drugs)

Histology

The histologic hallmarks of UIP, as seen in lung tissue under a microscope by a pathologist, are interstitial fibrosis in a "patchwork pattern", honeycomb change and fibroblast foci (see images below). Image:UIPlungbiopsy.jpg, Appearance of usual interstitial pneumonia (UIP) in a surgical lung biopsy at low magnification. The tissue is stained with hematoxylin (purple dye) and eosin (pink dye) to make it visible. The pink areas in this picture represent lung fibrosis (collagen stains pink). Note the "patchwork" (quilt-like) pattern of the fibrosis. Image:Honeycomb change.jpg, Appearance of honeycomb change in a surgical lung biopsy at low magnification. The dilated spaces seen here are filled with mucin. Hematoxylin-eosin stain, low magnification. Image:Fibroblast focus.jpg, A fibroblast focus in a surgical lung biopsy of UIP. Hematoxylin-eosin stain, high magnification. The white space to the left is an airspace. The pale area to the right is a fibroblast focus. It is an area of active fibroblast proliferation within the interstitium of the lung.

Differential diagnosis

The differential diagnosis includes other types of lung disease that cause similar symptoms and show similar abnormalities on chest radiographs. Some of these diseases cause fibrosis, scarring or honeycomb change. The most common considerations include: *

chronic hypersensitivity pneumonitis Hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis (EAA) is a syndrome caused by the repetitive inhalation of antigens from the environment in susceptible or sensitized people. Common antigens include molds, bacteria, bird dropping ...

non-specific interstitial pneumonia Non-specific interstitial pneumonia (NSIP) is a form of idiopathic interstitial pneumonia. Symptoms Symptoms include cough, difficulty breathing, and fatigue. Causes It has been suggested that idiopathic nonspecific interstitial pneumonia has a ...

sarcoidosis Sarcoidosis (also known as ''Besnier-Boeck-Schaumann disease'') is a disease involving abnormal collections of inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph nodes. Less commonly a ...

pulmonary Langerhans cell histiocytosis The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of ...

Management

Oxygen therapy may assist with daily living. In case of

, certain medications like

nintedanib Nintedanib, sold under the brand names Ofev and Vargatef, is an oral medication used for the treatment of idiopathic pulmonary fibrosis and along with other medications for some types of non-small-cell lung cancer. In March 2020, it was appro ...

and

pirfenidone Pirfenidone is a medication used for the treatment of idiopathic pulmonary fibrosis. It works by reducing lung fibrosis through downregulation of the production of growth factors and procollagens I and II. It was first approved in Japan for t ...

can help slow the progression. Lastly, lung transplants may help.

Prognosis

Regardless of cause, UIP is relentlessly progressive, usually leading to

respiratory failure Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...

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).

History

UIP, as a term, first appeared in the

pathology Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...

literature. It was coined by Averill Abraham Liebow.

References

External links

{{Respiratory pathology Pneumonia