Acute interstitial pneumonitis 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 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, pul ...

and a form of

acute respiratory distress syndrome Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin col ...

(ARDS) but it is distinguished from the ''chronic'' forms of interstitial pneumonia such as

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 ...

Symptoms and signs

The most common symptoms of acute interstitial pneumonitis are highly productive cough with expectoration of thick mucus,

fever Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...

, 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 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 ...

). Acute interstitial pneumonitis typically progresses rapidly, with hospitalization and mechanical ventilation often required only days to weeks after initial symptoms of

cough A cough is a sudden expulsion of air through the large breathing passages that can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three ph ...

, fever, and difficulties breathing develop.

Diagnosis

Rapid progression from initial symptoms to respiratory failure is a key feature. An X-ray that shows ARDS is necessary for diagnosis (fluid in the small air sacs ( alveoli) in both lungs). In addition, a

biopsy A biopsy is a medical test commonly performed by a surgeon, interventional radiologist, or an interventional cardiologist. The process involves extraction of sample cells or tissues for examination to determine the presence or extent of a d ...

of the lung that shows organizing

diffuse alveolar damage Diffuse alveolar damage (DAD) is a histologic term used to describe specific changes that occur to the structure of the lungs during injury or disease. Most often DAD is described in association with the early stages of acute respiratory distress s ...

is required for diagnosis. This type of alveolar damage can be attributed to nonconcentrated and nonlocalized alveoli damage, marked alveolar septal edema with inflammatory cell infiltration, fibroblast proliferation, occasional hyaline membranes, and thickening of the alveolar walls. The septa are lined with atypical, hyperplastic type II pneumocytes, thus leading to the collapse of airspaces. Other diagnostic tests are useful in excluding other similar conditions, but history, X-ray, and biopsy are essential. These other tests may include basic blood work, blood cultures, and

bronchoalveolar lavage Bronchoalveolar lavage (BAL) (also known as bronchoalveolar washing) is a diagnostic method of the lower respiratory system in which a bronchoscope is passed through the mouth or nose into an appropriate airway in the lungs, with a measured amoun ...

. The clinical picture is similar to ARDS, but AIP differs from ARDS in that the cause for AIP is not known. File:CRIM.PULMONOLOGY2012-678249.001.jpg, Acute interstitial pneumonia showing a marked reduction in lung capacity File:Acute interstitial pneumonia (AIP) Idiopathic DAD 3.jpg File:Acute interstitial pneumonia (AIP) Idiopathic DAD 2.jpg File:Acute interstitial pneumonia (AIP) Idiopathic DAD.jpg

Treatment

Treatment is primarily supportive. Management in an

intensive care unit 220px, Intensive care unit An intensive care unit (ICU), also known as an intensive therapy unit or intensive treatment unit (ITU) or critical care unit (CCU), is a special department of a hospital or health care facility that provides intensi ...

is required and the need for

mechanical ventilation Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move ai ...

is common. Therapy with

corticosteroids Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are in ...

is generally attempted, though their usefulness has not been established. The only treatment that has met with success to date is a

lung transplant Lung transplantation, or pulmonary transplantation, is a surgical procedure in which one or both lungs are replaced by lungs from a donor. Donor lungs can be retrieved from a living or deceased donor. A living donor can only donate one lung lobe ...

Prognosis

Sixty percent of people with acute interstitial pneumonitis will die in the first six months of illness. The median survival is months. However, most people who have one episode do not have a second. People who survive often recover lung function completely.

Epidemiology

Acute interstitial pneumonitis occurs most frequently among people older than forty years old. It affects men and women equally. There are no known risk factors; in particular,

smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...

is not associated with increased risk.

History

Acute interstitial pneumonitis was first described in 1935 by

Louis Hamman Louis Virgil Hamman (December 21, 1877 – April 28, 1946) was recognized as one of the great clinicians in his time. Early life Louis Virgil Hamman was born on December 21, 1877, in Baltimore, Maryland, to Agatha (née Haseneyer) and John A. Ha ...

and Arnold Rich, and given the name Hamman–Rich syndrome.

References

External links

* * {{DEFAULTSORT:Acute interstitial pneumonitis Respiratory diseases principally affecting the interstitium Ailments of unknown cause Syndromes affecting the lung