ArticlesOrganizing Pneumonia
Section snippets
Epidemiology
OP is considered to be a rare disease. A retrospective study showed that the incidence of COP was 1.10/100,000, whereas the incidence of SOP was 0.86/100,000, with an overall incidence of 1.96/100,000.2 This study also demonstrated a significant increase in the incidence of organizing pneumonias over the last 20 years. COP is not associated with race or gender.2., 3. The mean age of onset is in the fifth to sixth decade of life,4 although some cases have been reported in childhood.5 There are
Histology
The prominent histological finding in OP is patchy involvement of the pulmonary parenchyma by fibromyxoid, polypoid plugs of granulation tissue (also known as Masson bodies) within the alveoli and occasionally within the bronchioles (in which case the term bronchiolitis obliterans organizing pneumonia may be applied) (Figure 1). There is a mild interstitial infiltrate, associated with type II epithelial cell metaplasia. Foamy macrophages (macrophages that have ingested endogenous lipoid
Clinical Symptoms and Findings
The disease usually develops after a prodrome of a flu-like syndrome associated with fever, fatigue, nonproductive cough (70%), mild dyspnea (65%), and weight loss (60%), which lasts for several weeks. Radiographs typically show alveolar infiltrates (Figure 2). Antibiotic administration for a presumptive infectious pneumonia is ineffective. The diagnosis is typically not suspected for at least 4 to 10 weeks.10 Although many of the prodromal symptoms resolve, dyspnea worsens and usually becomes
Radiological Findings
There are 3 radiological patterns of OP, each associated with different clinical presentation.18., 19. The most common radiological pattern of COP is peripheral, bilateral, diffuse alveolar opacities. This pattern is often confused with infectious pneumonia. These opacities are usually located in the lower lung lobes, and they may be recurrent and migratory in up to 50% of the cases. High-resolution computed tomography (CT) detects such abnormalities in more than 90% of cases. Their density
Bronchoalveolar Lavage
The main role of bronchoalveolar lavage in the diagnosis of OP is to exclude infectious pneumonia and malignancy. There are no lavage findings that specifically confirm the diagnosis of OP.
Diagnosis
Although the typical clinical and radiological features may suggest the diagnosis of OP,25 histological confirmation is essential for the diagnosis and for the identification of causes of SOP (eg, malignancy). The location of the biopsy may be guided according to the high resolution CT findings.1
It is controversial whether transbronchial lung biopsy is adequate for the diagnosis of OP. Airspace organization or an organizing pneumonia pattern, with intraluminar buds of granulation tissue, may be
Causes of SOP
As already mentioned, Op may be either idiopathic (COP) or secondary (SOP).
Table 1 lists various etiologies for SOP. Although SOP can occur with any connective tissue disease, it is more commonly associated with dermatomyositis-polymyositis27 and rheumatoid arthritis.28 Numerous infectious pathogens are well-known causes of SOP, which usually represents an inflammatory sequela after the clearance of the infectious agent with appropriate chemotherapy.29 Interestingly, SOP can be associated with
Treatment
Spontaneous remission of organizing pneumonia is rare,12 and therefore the diagnosis of OP usually requires treatment if the patient is symptomatic. The standard treatment for OP is corticosteroids, which usually results in rapid clinical, radiological and functional improvement. However, the use of corticosteroids does not always result in complete resolution and relapses are common (see prognosis section below).6., 11. Furthermore, the numerous side effects of corticosteroids can complicate
Prognosis
The mortality of OP has been reported to vary from 5% to as high as 27%.3., 6., 7., 10., 17., 45. Mortality rates appear higher with SOP than COP.
Corticosteroid therapy results in complete recovery in up to 80% of patients within a few weeks to 3 months. The disease is persistent in the remainder.6., 7., 12., 45. The development of a reticulonodular pattern on high resolution CT is an indicator that organizing pneumonia is progressing to fibrosis.19., 46. Cases of spontaneous disease regression
Summary
Although relatively rare, OP is an important diagnosis for the clinician to consider for several reasons. First, the clinical presentation mimics pneumonia which may result in the administration of inappropriate antibiotics and a prolonged delay in diagnosis and treatment. Second, OP is associated with many specific causes (SOP) that may require therapy in order for the lung disease to be adequately treated. Third, COP is a cause of acute respiratory distress syndrome, and this would be an
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2021, Respiratory Medicine Case ReportsCitation Excerpt :It is defined histopathologically by intra-alveolar buds of granulation tissue within the lumen of distal pulmonary airspaces. OP can be either cryptogenic or secondary to different clinical conditions, as infections, connective tissue diseases, malignancies, organ transplants, radiotherapy or certain drugs [1,2]. Despite being nonspecific, its diagnosis can be made by the association of imaging and clinical criteria [3], in particular evidence of multiple bilateral and peripheral alveolar opacities after initial improvement of fever and dyspnea [4].
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2020, Surgical Pathology ClinicsCitation Excerpt :It is unclear whether this variant shows disease progression or not at this time. The differential diagnosis of OP can be broad, and includes cellular NSIP, DAD, infection,76 connective tissue disease manifesting in the lung,87 eosinophilic pneumonia,88 drug injury,89 radiation pneumonitis, and vasculitis. Important points in differential diagnosis of OP are shown in Table 5.