Hamman-Rich syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Hamman-Rich syndrome is a rare, severe lung disease which usually affects otherwise healthy individuals. HR syndrome is often categorized as both an interstitial lung disease and a form of acute respiratory distress syndrome (ARDS).
Historical Perspective
In 1935, Hamman and rich first described cases with rapidly progressing pulmonary fibrosis of unknown etiology. After that, the eponym, Hamman-Rich syndrome have been used to describe idiopathic pulmonary fibrosis. In 1975, Liebow came up with classification to distinguish between pulmonary fibrosis and idiopathic interstitial lung diseases. In 1986, Katzenstein coined the term acute interstitial pneumonitis. Further studies helped to differentiate acute interstitial pneumonitis from pulmonary fibrosis.
Classification
According to American Thoracic Society/European Respiratory Society (ATS/ERS) 2002 consensus, Acute interstitial pneumonitis is an entity of a group of Idiopathic interstitial lung diseases. The classification is based on clinical, radiological and histopathologic findings. The classification has been updated by ATS/ERS International multidisciplinary panel recently based on the literature review on idiopathic interstitial lung diseases published between 2000-2011.
Pathophysiology
Acute interstitial pneumonitis shows the histopathologic appearance of diffuse alveolar damage. On gross examination, lungs appear firm, heavy and have a dark red or beefy appearance and show irregular areas of consolidation and fibrosis. On microscopic examination, acute interstitial pneumonitis shows bilateral, temporal uniformity of the diffuse alveolar damage, hyaline membrane deposition and extensive fibroblastic and myofibroblastic proliferation.
Causes
There is no specific etiology (idiopathic), that is responsible for developing acute interstitial pneumonitis.
Differentiating [disease name] from other Diseases
Acute interstitial pneumonitis must be differentiated from other diseases that present with respiratory failure and diffuse infiltrates on chest radiographs. Some of the differentials include ARDS, acute eosinophilic pneumonitis, Infections, hypersensitivity pneumonitis, connective tissue diseases, and drug-induced lung toxicity.
Epidemiology and Demographics
- The prevalence of [disease name] is approximately [number or range] per 100,000 individuals worldwide.
- In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].
Age
Acute interstitial pneumonitis occur typically previously healthy individuals in the age group of 50 to 55years.
Gender
Acute interstitial pneumonitis affects men and women equally.
Race
In general there is no racial predilection to acute interstitial pneumonitis.
Risk Factors
- There are no established risk factors associated with acute interstitial pneumonitis.
Natural History, Complications and Prognosis
- The majority of patients with [disease name] remain asymptomatic for [duration/years].
- Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
- If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
- Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
- Prognosis is generally [excellent/good/poor], and the [1/5/10year mortality/survival rate] of patients with [disease name] is approximately [#%].
Diagnosis
Diagnostic Criteria
- Abrupt onset of respiratory symptoms resulting in acute respiratory failure
- Chest radiographs show bilateral lung infiltrates
- The absence of an identifiable etiology
- Absence of predisposing condition
- Organising diffuse alveolar damage seen on histopathological examination
Symptoms
- Patients with acute interstitial pneumonitis usually present with flu-like viral illness or upper respiratory tract infection, which progresses very rapidly to acute respiratory failure. Common symptoms include fatigue, headache, myalgia, cough, fever, and dyspnea. The acute onset of symptoms is characteristic of acute interstitial pneumonitis.
Physical Examination
- Patients with [disease name] usually appear [general appearance].
- Physical examination may be remarkable for:
- [finding 1]
- [finding 2]
- [finding 3]
- [finding 4]
- [finding 5]
- [finding 6]
Laboratory Findings
- There are no diagnostic laboratory findings associated with acute interstitial pneumonitis. However, routine laboratory tests may help in identifying alternative diagnoses rather than making a diagnosis of acute interstitial pneumonitis, include abnormal arterial blood gases, physiologic lung testing, complete blood count, and sputum examination, and microbiologic tests.
Imaging Findings
- Chest radiograph of patients with Acute interstitial pneumonitis shows bilateral airspace opacifications.
- Most of the patients with acute interstitial pneumonitis on HRCT will show bilateral ground-glass attenuation, traction bronchiectasis, airspace consolidation, architectural distortion. This pattern of abnormality is typically found in acute interstitial pneumonitis but it is not diagnostic.
Other Diagnostic Studies
- Bronchioalveolar lavage and surgical lung biopsy can be helpful in diagnosing other diseases that causing diffuse alveolar damage that present same as acute interstitial pneumonitis.
Treatment
Medical Therapy
- There is no effective treatment for acute interstitial pneumonitis, Management in general includes supportive therapy and administration of glucocorticosteroids and Immunosuppressive agents
Surgery
- Lung transplantation may be considered as an alternative treatment for patients with acute interstitial pneumonitis if the conventional therapy fails.
Prevention
- There are no sufficient guidelines for the primary prevention of acute interstitial pneumonitis. However, preventing general triggering agents that leads to fibrotic changes in lungs including smoking cessation and vaccination against influenza may be helpful in preventing pulmonary fibrosis and other idiopathic fibrotic lung conditions