Organising pneumonia (OP) is an inflammatory disorder involving both the peripheral bronchioles and alveoli simultaneously. It has distinctive radiographic findings, histological features, and response to corticosteroids (unlike usual interstitial pneumonia).
OP may be caused by multiple insults such as medication, infection, rheumatological disease, autoimmune disease, post-transplantation, radiation, and environmental causes. In cryptogenic organising pneumonia, a cause cannot be elicited after a careful history, examination and pertinent laboratory studies.
High-resolution chest computed tomography scan shows bilateral patchy triangular ground glass opacities with air bronchograms usually located peripherally.
Most often, diagnosis is made using clinico-radiological criteria and usually in the setting of a multidisciplinary team. However, lung biopsy may be required to establish the definitive diagnosis in patients with unusual findings.
Cryptogenic OP may require treatment, and prednisolone is the most commonly used drug.
For patients with secondary OP, primary management is removal of the inciting cause or treatment of the underlying disease. In some patients, corticosteroids may be indicated.
Organising pneumonia (OP) is defined as organised polypoid granulation tissue in the terminal bronchioles, alveolar ducts and alveoli; it has distinctive radiographic findings, histological features, and response to therapy. The term cryptogenic is applied when a causative factor cannot be found.
OP was previously called bronchiolitis obliterans with organising pneumonia (BOOP) but this led to some confusion with the entirely separate disease bronchiolitis obliterans. Hence, a revision of the nomenclature to organising pneumonia, cryptogenic and secondary. Some clinicians still adhere to the earlier nomenclature. The term cryptogenic organising pneumonia (COP) is a general term referring to organised inflammatory process in the alveoli from an unknown cause. COP is the preferred term because it captures an 'acinar' rather than an airway disease, and BOOP may be confused with obliterative bronchiolitis.
The following are a few differences between obliterative bronchiolitis, where there is obstruction of the bronchioles due to inflammation, and organising pneumonia. Wheezing is not a common symptom of OP; crackles, and not wheezes, are heard by auscultation in OP. The FEV1/FVC ratio is normal or slightly increased in OP, not decreased as in airway obstructive diseases and the radiographic findings show bilateral patchy infiltrates, not normal or hyperinflation seen in airflow obstructive diseases.
History and exam
Key diagnostic factors
- presence of risk factors
- flu-like illness with low-grade fever, fatigue, and arthralgia
Other diagnostic factors
- shortness of breath
- bilateral crackles
- infectious pneumonia
- connective tissue diseases
- immunological diseases and inflammatory bowel disease
- organ transplantation
- medication use
- breast radiotherapy
- exposure to toxins
1st investigations to order
- chest x-ray
- high-resolution chest CT scan (HRCT)
- erythrocyte sedimentation rate
Investigations to consider
- C-reactive protein
- sputum culture
- atypical viral screen
- pulmonary function tests
- surgical lung biopsy
- creatine kinase
- general autoimmune and myositis profile
- positron emission tomography (PET) scan
rapidly progressive OP
recurrent OP, rapidly progressive
recurrent OP, not rapidly progressive
- Nodular sarcoidosis
- Chronic eosinophilic pneumonia (CEP)
- Non-specific interstitial pneumonia (NSIP)
- Korean guidelines for diagnosis and management of interstitial lung diseases: part 4. cryptogenic organizing pneumonia
- An official American Thoracic Society/European Respiratory Society statement: update of the international multidisciplinary classification of the idiopathic interstitial pneumonias
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