Bronchiolitis obliterans organizing pneumonia
Encyclopedia
Bronchiolitis obliterans organizing pneumonia (BOOP) is an inflammation
of the bronchiole
s (bronchiolitis
) and surrounding tissue in the lung
s. It is an non infectious pneumonia
. BOOP is often caused by a pre-existing chronic inflammatory disease like rheumatoid arthritis
. BOOP can also be a side effect of certain medicinal drugs, e.g. amiodarone
. BOOP was discovered by Dr. Gary Epler in 1985.
It is also known as cryptogenic organizing pneumonia (COP), and some sources recommend using the latter term, to reduce confusion with bronchiolitis obliterans
.
The clinical features and radiological imaging
resemble infectious pneumonia
. However, diagnosis is suspected after there is no response to multiple antibiotic
s, and blood and sputum
cultures are negative for organism
s.
Almost 75% of people have symptoms for less than two months before seeking medical attention. A flu-like illness, with a cough, fever, a feeling of illness (malaise), fatigue, and weight loss heralds the onset in about 40% of patients. Doctors do not find any specific abnormalities on routine laboratory tests or on a physical examination, except for the frequent presence of crackling sounds (called rales) when the doctor listens with a stethoscope. Pulmonary function tests usually show that the amount of air the lungs can hold is below normal. The amount of oxygen in the blood is often low at rest and is even lower with exercise.
Plain chest radiography shows normal lung volumes
, with characteristic patchy unilateral or bilateral consolidation. Small nodular opacities occur in up to 50% of patients and large nodules in 15%. On high resolution computed tomography, airspace consolidation with air bronchograms is present in more than 90% of patients, often with a lower zone predominance A subpleural or peribronchiolar distribution is noted in up to 50% of patients. Ground glass appearance or hazy opacities associated with the consolidation are detected in most patients.
Pulmonary physiology is restrictive with a reduced diffusion capacity of the lung for carbon monoxide
(DLCO). Airflow limitation is uncommon; gas exchange is usually abnormal and mild hypoxemia
is common. Bronchoscopy
with bronchoalveolar lavage
reveals up to 40% lymphocytes, along with more subtle increases in neutrophils and eosinophils. In patients with typical clinical and radiographic features, a transbronchial biopsy that shows the pathologic pattern of organizing pneumonia and lacks features of an alternative diagnosis is adequate to make a tentative diagnosis and start therapy. On surgical lung biopsy, the histopathologic pattern is organizing pneumonia with preserved lung architecture; this pattern is not exclusive to BOOP and must be interpreted in the clinical context.
therapy. A standardized approach to dosing starting at 0.75 mg/kg and weaning over 24 weeks has been shown to reduce total corticosteroid exposure without affecting outcome.
About two thirds of patients recover with corticosteroid therapy: the usual steroid administered is prednisolone in Europe and prednisone in the USA; these differ by only one functional group and have the same clinical effect. The steroid is initially administered in high dosage, typically 50 mg per day tapering down to zero over a six-month to one-year period. If the steroid treatment is halted too quickly the disease may return. Other drugs must be taken to counteract side effects of the steroid.
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the bronchiole
Bronchiole
The bronchioles or bronchioli are the first airway branches that no longer contain cartilage or glands in their submucosa. They are branches of the bronchi.The bronchioles terminate by entering the circular sacs called alveoli.- Structure :...
s (bronchiolitis
Bronchiolitis
Bronchiolitis is inflammation of the bronchioles, the smallest air passages of the lungs. It usually occurs in children less than two years of age and presents with coughing, wheezing, and shortness of breath. This inflammation is usually caused by viruses...
) and surrounding tissue in the lung
Lung
The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...
s. It is an non infectious pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
. BOOP is often caused by a pre-existing chronic inflammatory disease like rheumatoid arthritis
Rheumatoid arthritis
Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...
. BOOP can also be a side effect of certain medicinal drugs, e.g. amiodarone
Amiodarone
Amiodarone is an antiarrhythmic agent used for various types of tachyarrhythmias , both ventricular and supraventricular arrhythmias. Discovered in 1961, it was not approved for use in the United States until 1985...
. BOOP was discovered by Dr. Gary Epler in 1985.
It is also known as cryptogenic organizing pneumonia (COP), and some sources recommend using the latter term, to reduce confusion with bronchiolitis obliterans
Bronchiolitis obliterans
Bronchiolitis obliterans , also called obliterative bronchiolitis and constrictive bronchiolitis , is a rare and life-threatening form of non-reversible obstructive lung disease in which the bronchioles are compressed and narrowed by fibrosis and/or inflammation...
.
The clinical features and radiological imaging
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...
resemble infectious pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
. However, diagnosis is suspected after there is no response to multiple antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
s, and blood and sputum
Sputum
Sputum is mucus that is coughed up from the lower airways. It is usually used for microbiological investigations of respiratory infections....
cultures are negative for organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s.
Terminology
"Organizing" refers to unresolved pneumonia (in which the alveolar exudate persists and eventually undergoes fibrosis) in which fibrous tissue forms in the alveoli. The phase of resolution and/or remodeling following bacterial infections is commonly referred to as organizing pneumonia, both clinically and pathologically.Signs and symptoms
- cough
- dyspneaDyspneaDyspnea , shortness of breath , or air hunger, is the subjective symptom of breathlessness.It is a normal symptom of heavy exertion but becomes pathological if it occurs in unexpected situations...
- influenza-like symptoms
- febrile illness
- widespread crackles
- mild resting hypoxemia
Cause
COP/BOOP may be triggered by infections from bacteria, viruses and parasites, drugs, or toxic fumes. It was identified in 1985, although its symptoms had been noted before but not recognised as a separate lung disease. The risk of BOOP is higher for people with inflammatory diseases like lupus, rheumatoid arthritis, and scleroderma.Diagnosis
On clinical examination, crackles are common, and more rarely, patients may have clubbing. Laboratory findings are nonspecific.Almost 75% of people have symptoms for less than two months before seeking medical attention. A flu-like illness, with a cough, fever, a feeling of illness (malaise), fatigue, and weight loss heralds the onset in about 40% of patients. Doctors do not find any specific abnormalities on routine laboratory tests or on a physical examination, except for the frequent presence of crackling sounds (called rales) when the doctor listens with a stethoscope. Pulmonary function tests usually show that the amount of air the lungs can hold is below normal. The amount of oxygen in the blood is often low at rest and is even lower with exercise.
Imaging
The chest x-ray is distinctive with features that appear similar to an extensive pneumonia, with both lungs showing widespread white patches. The white patches may seem to migrate from one area of the lung to another as the disease persists or progresses. Computed Tomography (CT) may be used to confirm the diagnosis. Often the findings are typical enough to allow the doctor to make a diagnosis without ordering additional tests. To confirm the diagnosis, a doctor may perform a lung biopsy using a bronchoscope. Many times, a larger specimen is needed and must be removed surgically.Plain chest radiography shows normal lung volumes
Lung volumes
Lung volumes and lung capacities refer to the volume of air associated with different phases of the respiratory cycle. Lung volumes are directly measured...
, with characteristic patchy unilateral or bilateral consolidation. Small nodular opacities occur in up to 50% of patients and large nodules in 15%. On high resolution computed tomography, airspace consolidation with air bronchograms is present in more than 90% of patients, often with a lower zone predominance A subpleural or peribronchiolar distribution is noted in up to 50% of patients. Ground glass appearance or hazy opacities associated with the consolidation are detected in most patients.
Pulmonary physiology is restrictive with a reduced diffusion capacity of the lung for carbon monoxide
DLCO
DLCO is the extent to which oxygen passes from the air sacs of the lungs into the blood. Commonly, it refers to the test used to determine this parameter. It was introduced in 1909....
(DLCO). Airflow limitation is uncommon; gas exchange is usually abnormal and mild hypoxemia
Hypoxemia
Hypoxemia is generally defined as decreased partial pressure of oxygen in blood, sometimes specifically as less than or causing hemoglobin oxygen saturation of less than 90%.-Distinction from anemia and hypoxia:...
is common. Bronchoscopy
Bronchoscopy
Bronchoscopy is a technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument is inserted into the airways, usually through the nose or mouth, or occasionally through a tracheostomy. This allows the practitioner to examine the patient's airways for...
with 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...
reveals up to 40% lymphocytes, along with more subtle increases in neutrophils and eosinophils. In patients with typical clinical and radiographic features, a transbronchial biopsy that shows the pathologic pattern of organizing pneumonia and lacks features of an alternative diagnosis is adequate to make a tentative diagnosis and start therapy. On surgical lung biopsy, the histopathologic pattern is organizing pneumonia with preserved lung architecture; this pattern is not exclusive to BOOP and must be interpreted in the clinical context.
Treatment
Most patients recover with corticosteroidCorticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
therapy. A standardized approach to dosing starting at 0.75 mg/kg and weaning over 24 weeks has been shown to reduce total corticosteroid exposure without affecting outcome.
About two thirds of patients recover with corticosteroid therapy: the usual steroid administered is prednisolone in Europe and prednisone in the USA; these differ by only one functional group and have the same clinical effect. The steroid is initially administered in high dosage, typically 50 mg per day tapering down to zero over a six-month to one-year period. If the steroid treatment is halted too quickly the disease may return. Other drugs must be taken to counteract side effects of the steroid.