Acute interstitial pneumonia

Other Names: Acute interstitial pneumonitis; Hamman-Rich syndrome

Acute interstitial pneumonia (AIP) is a rare and serious condition that affects the lungs. Acute interstitial pneumonia (AIP - also known as Hamman-Rich syndrome) is an acute, rapidly progressive idiopathic pulmonary disease that often leads to fulminant respiratory failure and acute respiratory distress syndrome (ARDS).

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Epidemiology

The mean age of patients with AIP is around 55. There is no sex predilection.

Cause

The underlying cause of AIP is unknown.

Inheritance

Most cases occur sporadically in people with no family history of the condition.

Signs and symptoms

The signs and symptoms generally develop and progress rapidly. In the early stages of the condition, affected people may experience upper respiratory and/or viral-like symptoms such as cough, shortness of breath, and fever. This is followed by the rapid onset of respiratory failure and the need for mechanical ventilation in the majority of cases.

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Bronchiectasis(Permanent enlargement of the airways of the lungs)
• Dyspnea(Trouble breathing)
• Ground-glass opacification on pulmonary HRCT
• Hypoxemia(Low blood oxygen level)
• Interlobular septal thickening on pulmonary HRCT
• Nodular pattern on pulmonary HRCT
• Peribronchovascular interstitial thickening
• Pulmonary infiltrates(Lung infiltrates)
• Respiratory failure
• Reticulonodular pattern on pulmonary HRCT

30%-79% of people have these symptoms

• Crackles
• Cyanosis(Blue discoloration of the skin)
• Decreased DLCO
• Fatigue(Tired)
• Fever
• Hypertension
• Nonproductive cough(Dry cough)
• Pleural effusion(Fluid around lungs)
• Tachypnea(Increased respiratory rate or depth of breathing)

Diagnosis

• Patients with Acute Interstitial Pneumonia are at risk of rapid respiratory decompensation. Vital signs should be monitored closely. Arterial blood gases can identify the severity of hypoxemia and the need for mechanical ventilation.
• Chest X-ray usually shows a pattern that is similar to ARDS, which is a bilateral air-space diffuse opacities. Therefore, ruling out cardiac causes of pulmonary edema is essential. Echocardiography is needed to rule out underlying cardiomyopathy or valve dysfunction.
• CT findings can also show traction bronchiectasis, indicating progression from the exudative phase to the proliferative fibrotic phase.
• Laboratory workup should include screening for autoimmune and connective tissue diseases that might be associated with lung disease, starting from rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE) to dermatomyositis and Sjogren syndrome.
• Microbiologic workup should include blood and sputum culture. Influenza screening is important, as well as serology for atypical organisms and fungus. Legionella is an atypical organism that can be detected on urine antigen test. Bronchoscopy with bronchoalveolar lavage (BAL) is needed to exclude diffuse alveolar hemorrhage (DAH), eosinophilia, or malignant infiltrates. In acute interstitial pneumonia, BAL results are usually non-specific with neutrophilia and scattered atypical type II pneumocytes. Bronchoscopy also helps in obtaining respiratory samples for culture in the absence of sputum production. The sample should be sent for cell count and cytology, cultures, and Pneumocystis jirovecii immunofluorescence.
• If the previous workup fails to achieve an alternative diagnosis, lung biopsy might be indicated. Lung biopsy might also reveal different etiologies like caseating granulomas (tuberculosis), non-caseating granulomas (sarcoidosis), necrosis (vasculitis), abscesses, or viral inclusion.
• Acute interstitial pneumonia is an idiopathic disease. After excluding other causes of ARDS, pathologic confirmation of idiopathic DAD is necessary to establish the diagnosis.

Treatment

• There is no proven treatment in AIP. Management is largely based on supportive care. Adequate oxygenation often cannot be achieved without mechanical ventilation.Ventilator management mainly focuses on low tidal volume ventilation and other advanced ventilator modalities such as those used in ARDS.Glucocorticoid therapy and other immunosuppressive therapies are often used; however, the benefits of these treatments remain unclear.
• Broad-spectrum antibiotics are recommended initially until infectious etiology is excluded.
• Extracorporeal membrane oxygenation (ECMO) and lung transplantation should be considered for appropriate candidates after failing conventional therapy.

Prognosis

Sixty percent of people with acute interstitial pneumonitis will die in the first six months of illness.

NIH genetic and rare disease info

• NIH info on Acute interstitial pneumonia

Acute interstitial pneumonia is a rare disease.

Acute interstitial pneumonia Resources
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