Bronchiolitis Obliterans With Organizing Pneumonia, Idiopathic
Idiopathic bronchiolitis obliterans with organizing pneumonia (BOOP), also known as cryptogenic organizing pneumonia, is one of several types of bronchiolitis obliterans. "Bronchiolitis obliterans" is a generic term used to describe an inflammatory disease of the small airways. "Organizing pneumonia" refers to unresolved pneumonia, in which inflammatory alveolar exudate persists and eventually undergoes fibrosis.
Although BOOP was first described in 1901, confusing terminology and pathology that overlapped other diseases of the small airways kept it from being sufficiently recognized until the mid1980s, when it was classified as a distinct clinical entity. Since that time, BOOP has been diagnosed with increasing frequency, although much debate still exists about the various pathologies and classifications of bronchiolitis obliterans.
Most patients with BOOP are between ages 50 and 60. Incidence is equally divided between men and women. A smoking history doesn't seem to increase the risk of developing BOOP.
BOOP has no known cause. However, other forms of bronchiolitis obliterans and organizing pneumonia may be associated with specific diseases or situations, such as bone marrow, heart, or heart-lung transplantation; collagen vascular diseases, such as rheumatoid arthritis and systemic lupus erythematosus; inflammatory diseases, such as Crohn's disease, ulcerative colitis, and polyarteritis nodosa; bacterial, viral, or mycoplasmal respiratory infections; inhalation of toxic gases; and drug therapy with amiodarone, bleomycin, penicillamine, or lomustine.
Signs and symptoms
The presenting symptoms of BOOP are usually subacute, with a flu like syndrome of fever, persistent and nonproductive cough, dyspnea (especially on exertion), malaise, anorexia, and weight loss lasting from several weeks to several months. Physical assessment findings may reveal dry crackles as the only abnormality. Less common symptoms include a productive cough, hemoptysis, chest pain, generalized aching, and night sweats.
Diagnosis begins with a thorough patient history meant to exclude any known cause of bronchiolitis obliterans or diseases with a pathology that includes an organizing pneumonia pattern.
Lung biopsy, thoracoscopy, or bronchoscopy is required to confirm the diagnosis of BOOP. Pathologic changes In lung tissue include plugs of connective tissue in the lumen of the bronchinics, alveolar ducts, and alveolar spaces.
These changes may occur in other types of bronchiolitis and in other diseases that cause organizing pneumonia. They also differentiate BOOP from constrictive bronchiolitis, characterized by ; Inflammation and fibrosis that surround and may narrow or completely obliternle the bronchiolar airways. Although the pathologic findings in proliferative and constrictive bronchiolitis are different, the causes and presentations may overlap. Any known cause of bronchiolitis obliterans or organizing pneumonia must be ruled out before the diagnosis of BOOP is made.
Corticosteroids are the current treatment for BOOP, although the ideal dosage and duration of treatment remain topics of discussion. In most cases, treatment begins with 1 mg/kg/day of prednisone for at least several days to several weeks; the dosage is then gradually reduced over several months to a year, depending on the patient's response. Relapse is common when steroids are tapered off or stopped but usually can be reversed when steroids are increased or resumed. Occasionally, a patient may need to continue corticosteroids indefinitely.
Immunosuppressant-cytotoxic drugs, such as cyclophosphamide, have been used in the few cases in which the patient couldn't tolerate or was unresponsive to corticosteroids.
Oxygen is used to correct hypoxemia. The patient may need either no oxygen or a small amount of oxygen at rest and a greater amount when he exercises. Other treatments vary, depending on the patient's symptoms, and may include inhaled bronchodilators, cough suppressants, and bronchial hygiene therapies.
BOOP is responsive to treatment and usually can be completely reversed with corticosteroid therapy. However, a few deaths have been reported, particularly in patients who had more widespread pathologic changes in the lungs or patients who developed opportunistic infections or other complications related to steroid therapy.
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