Description

• A primary or secondary process of the lungs characterized by granulationlike tissue involving the distal airways and alveoli
• Bronchiolitis obliterans and organizing pneumonia (BOOP) is a restrictive problem that is completely reversible, whereas bronchiolitis obliterans is an obstructive problem that causes permanent lung damage.
• A specific reaction of lung tissue to a variety of injuries
• It may occur as patchy infiltrates, or it may be nodular or secondary to another lung disease.
• May also appear to be a migrating process
• May have a gradual or sudden onset
• Lungs show a pattern of multiple patchy pneumonia, which are seen on the chest x-ray (CXR) as patchy alveolar or ground-glass, opacifications, with or without interstitial infiltrates; there may be air bronchograms as well.
• Most cases will respond to corticosteroids, which may have to be given for a year or more.
• Synonym(s): Intraluminal fibrosis of distal airways; Idiopathic bronchiolitis obliterans and organizing pneumonitis (BOOP); Cryptogenic organizing pneumonia; Obliterative bronchiolitis

Geriatric Considerations
More common than originally thought and may be sudden and very severe

• Characteristics include delayed recovery, persistent cough, crackles, or wheezing after pneumonia.
• Laboratory findings generally not helpful
• Imaging shows: Ventilation-perfusion ratio-matched defects; high-resolution CT, bronchiectasis, bronchogram, pruned tree appearance
• Diagnosis confirmed by biopsy

Epidemiology

• Incidence/Prevalence in the US: Estimated at 0.01%, but may be underdiagnosed.
• Predominant age: Reported cases range age 0–70; most commonly seen in ages 40–60s

Prevalence
Unknown

Risk Factors

• AIDS
• Immunocompromised patients, including transplant recipients
• Smoking

Genetics
No known genetic component

General Prevention

Except for prevention of relapse, none known

Etiology

Idiopathic: A complex response to a variety of injuries such as toxic inhalation, postmycoplasma, viral and bacterial infection, aspiration, immunologic factors, drugs

Pediatric Considerations
In the pediatric nontransplant recipient population, adenovirus infection is the most common cause of bronchiolitis obliterans (1).

Commonly Associated Conditions

• Drug-induced pneumonitis:
  • Paraquat poisoning
  • Amiodarone toxicity
  • Acebutolol toxicity
  • Amphotericin B
  • Bleomycin
  • Carbamazepine
  • Cephalosporins
  • Gold
  • Minocycline
  • Nitrofurantoin
  • Phenytoin
  • Sulfamethoxypyridazine
  • Sulfasalazine
  • Ticlopidine
  • Freebase cocaine pulmonary toxicity
  • Overdose of L-tryptophan
• Infections:
  • Chronic infectious pneumonia
  • Malaria
  • Chlamydia
  • Legionella
  • Mycoplasma
  • Pneumocystis
  • Cryptococcus
• Immunocompromise: Bone marrow, lung, renal, transplantation
• Connective tissue diseases:
  • Rheumatic lung
  • Sjögren syndrome
  • Polymyositis
  • Scleroderma
  • Essential mixed cryoglobulinemia
• Miscellaneous:
  • Cystic fibrosis
  • Bronchopulmonary dysplasia
  • Renal failure
  • Congestive heart failure (CHF)
  • Adult respiratory distress syndrome
  • Chronic eosinophilic pneumonia
  • Hypersensitivity pneumonitis
  • Histiocytosis X
  • Sarcoidosis
  • Pneumoconioses
• Radiation pneumonitis