Acute interstitial pneumonitis (also known as acute interstitial pneumonia or Hamman–Rich syndrome) is a rare, severe lung disease which usually affects otherwise healthy individuals.

As of 2010, there is no known cause or treatment.

Acute interstitial pneumonitis is often categorized as both an interstitial lung disease and a form of acute respiratory distress syndrome

Acute respiratory distress syndrome

Acute respiratory distress syndrome , also known as respiratory distress syndrome or adult respiratory distress syndrome is a serious reaction to various forms of injuries to the lung....

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

Idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis is a chronic, progressive form of lung disease characterized by fibrosis of the supporting framework of the lungs...

.

Symptoms

The most common symptoms of acute interstitial pneumonitis are cough

Cough

A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...

, fever

Fever

Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

, and difficulties breathing. These often occur over a period of one to two weeks before medical attention is sought. Difficulties breathing can quickly progress to an inability to breathe without support (respiratory failure

Respiratory failure

The term respiratory failure, in medicine, is used to describe inadequate gas exchange by the respiratory system, with the result that arterial oxygen and/or carbon dioxide levels cannot be maintained within their normal ranges. A drop in blood oxygenation is known as hypoxemia; a rise in arterial...

).

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

Cough

A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes...

, fever

Fever

Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...

, 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

Biopsy

A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...

 of the lung that shows organizing diffuse alveolar damage

Diffuse alveolar damage

Diffuse alveolar damage is a histological pattern in lung disease. It is seen in acute respiratory distress syndrome , transfusion related acute lung injury and acute interstitial pneumonia .-Prevalence:...

 is required for diagnosis. 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

Bronchoalveolar lavage is a medical procedure in which a bronchoscope is passed through the mouth or nose into the lungs and fluid is squirted into a small part of the lung and then recollected for examination. BAL is typically performed to diagnose lung disease...

.
The clinical picture is similar to ARDS, but AIP differs from ARDS in that the cause for AIP is not known.

Treatment

Treatment is primarily supportive. Management in an intensive care unit

Intensive Care Unit

thumb|220px|ICU roomAn intensive-care unit , critical-care unit , intensive-therapy unit/intensive-treatment unit is a specialized department in a hospital that provides intensive-care medicine...

 is required and the need for mechanical ventilation

Mechanical ventilation

In medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing. This may involve a machine called a ventilator or the breathing may be assisted by a physician, respiratory therapist or other suitable person compressing a bag or set of bellows...

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

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

Tobacco smoking

Tobacco smoking is the practice where tobacco is burned and the resulting smoke is inhaled. The practice may have begun as early as 5000–3000 BCE. Tobacco was introduced to Eurasia in the late 16th century where it followed common trade routes...

 is not associated with increased risk.

Prognosis

Sixty percent of people with acute interstitial pneumonitis will die in the first six months of illness. The median survival is 1½ months.

However, most people who have one episode do not have a second. People who survive often recover lung function completely.

History

Acute interstitial pneumonitis was first described in 1935 by Louis Hamman

Louis Hamman

Louis Virgil Hamman, M.D. was recognized as one of the great clinicians in his time.He was graduated M.D...

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