What are the different presentations of cryptogenic organizing pneumonia (COP)?

From the Guidelines

Organizing pneumonia can present in several different forms, including cryptogenic organizing pneumonia (COP), secondary organizing pneumonia, focal organizing pneumonia, and acute fibrinous organizing pneumonia (AFOP), each with distinct clinical and radiological features. The most common presentation is COP, previously known as bronchiolitis obliterans organizing pneumonia (BOOP), which is idiopathic in nature 1. Secondary organizing pneumonia can occur in association with connective tissue diseases like rheumatoid arthritis and systemic lupus erythematosus, drug reactions, infections, aspiration, and radiation therapy. Focal organizing pneumonia may present as a solitary nodule or mass, mimicking lung cancer. AFOP is a rare, severe variant characterized by intra-alveolar fibrin deposition.

Some key features of organizing pneumonia include:

• Patchy airspace consolidation, ground glass opacities, small nodular opacities, and bronchial wall thickening and dilation on HRCT scans 1
• A uniform, recent temporal appearance to the changes, with a patchy and peribronchiolar distribution, and lesions usually located within the airspace 1
• The presence of granulation tissue plugs (Masson bodies) within small airways and alveolar ducts, which is a hallmark of the disease 1
• Clinical improvement often seen within days to weeks with corticosteroid treatment, but relapses can occur in up to one-third of patients, especially during steroid tapering 1

Treatment typically involves corticosteroids, with prednisone 0.5-1 mg/kg/day for 1-3 months, followed by a gradual taper over 6-12 months 1. For steroid-resistant cases, immunosuppressants like cyclophosphamide, azathioprine, or mycophenolate mofetil may be considered. The pathophysiology involves an inflammatory response to lung injury, leading to the formation of granulation tissue plugs (Masson bodies) within small airways and alveolar ducts.

It's worth noting that the diagnosis of organizing pneumonia can be challenging, and it's essential to consider other conditions that may present with similar clinical and radiological features, such as hypersensitivity pneumonitis 1. However, the presence of characteristic histopathological features, such as the formation of granulation tissue plugs and the absence of granulomatous inflammation, can help establish the diagnosis of organizing pneumonia.

From the Research

Different Presentations of Organizing Pneumonia

Organizing pneumonia can present in various forms, including:

• Cryptogenic organizing pneumonia (COP) 2, 3
• Secondary forms of organizing pneumonia (OP), which occur in association with identifiable medical conditions such as infections, drugs, connective tissue disorders, and radiation 2, 4, 3
• Rapidly progressive, corticosteroid-resistant, and poor prognostic forms of OP, which are more frequently reported in secondary OP 2, 3
• Organizing pneumonia as a late phase complication of COVID-19, responding dramatically to corticosteroids 5

Characteristics of Different Presentations

The different presentations of organizing pneumonia have distinct characteristics, including:

• COP is considered to have a good prognosis and is corticosteroid responsive, but approximately 70% of patients relapse even during initial treatment 2, 3
• Secondary OP often coexists with other interstitial pneumonias, especially when associated with connective tissue diseases, and may have a more aggressive clinical behavior due to tissue sampling error or incorrect morphologic diagnosis 2, 3
• Organizing pneumonia secondary to COVID-19 may benefit from high-dose corticosteroids as an adjuvant therapy 5
• The duration of treatment with corticosteroids is longer for patients with COP compared to those with secondary BOOP 4

Treatment and Outcomes

The treatment and outcomes of different presentations of organizing pneumonia vary, including:

• Corticosteroids are the standard therapy for organizing pneumonia, but the optimal treatment regimen and duration are unclear 6, 2, 3
• Secondary non-steroidal agents such as cyclophosphamide, azathioprine, and cyclosporin have been used in combination with corticosteroids for steroid-resistant patients, with good clinical outcomes reported 2, 3
• The prognosis and treatment outcomes of organizing pneumonia can be influenced by the underlying condition, with secondary OP often having a poorer prognosis than COP 2, 4, 3