Cryptogenic organizing pneumonia (COP) 

Catharine Thomas, Consultant Physiotherapist, Tameside Hospital NHS FT

Cryptogenic organizing pneumonia (COP), the idiopathic form of organizing pneumonia (formerly called bronchiolitis obliterans organizing pneumonia or BOOP), is a type of diffuse interstitial lung disease that affects the distal bronchioles, respiratory bronchioles, alveolar ducts, and alveolar walls The primary area of injury is within the alveolar wall.

Disease onset is typically in the fifth or sixth decades of life with men and women affected equally. Most patients are symptomatic for less than two months and have a clinical presentation that mimics community-acquired pneumonia (e.g., cough, dyspnoea with exertion, weight loss). Approximately half of cases are heralded by a flu-like illness.

History

• Cough, dyspnoea, fever and malaise that are of relatively short duration (e.g., weeks to months)
• In almost 3/4 of the patients, symptoms are present for less than two months
• In 50%, the onset is heralded by the acute onset of a flu-like illness with fever, malaise, fatigue, and cough.

The most common features of the history at presentation:

• Persistent non productive cough (72%)
  
• Dyspnoea (66%)
  
• Fever (51%)
  
• Malaise (48%)
• Weight loss of greater than 10 pounds (57%)
• Hemoptysis is rarely reported as a presenting manifestation of COP.

Examination

•  Inspiratory crackles (74 %)
• Wheezing is rare and, when present, is heard in combination with crackles;
• Clubbing is seen in less than 5 percent of cases
•  A normal pulmonary examination is found in 25% of patients  

As with all patients who present with interstitial lung disease, the history should include questions about any symptoms or history suggestive of connective tissue disease (eg, arthralgias, dry eyes, dry mouth, muscle weakness, numbness, tingling), current and recent medications, and history of exposure to therapeutic irradiation, fumes, or dusts..)

Chest imaging

The most common chest imaging features of COP are:

• Multiple ground-glass or consolidative opacities.
• Peripheral distribution of the opacities
  
• Recurrent or migratory pulmonary opacities are common (up to 50 percent of subjects in some series)
  
• Rarely, unilateral consolidative and ground-glass opacities
  
• Rarely, irregular linear or nodular opacities as the only radiographic manifestations
  
• Other rare radiographic abnormalities include pleural effusion, pleural thickening, hyperinflation, and cavities
  

CXR of a forty-eight year old woman with an eight week history of cough, dyspnea with exertion, fatigue, and slight weight loss. PA chest radiograph reveals bilateral volume loss with reticular opacities at both bases (reproduced with permission).

High Resolution CT Thorax of a forty-eight-year-old woman with an eight-week history of cough, dyspnea with exertion, fatigue, and slight weight loss. High resolution CT scan shows right lower lobe reticular and hazy opacities that are subpleural (reproduced with permission).

Pulmonary function tests

Pulmonary functiont esting usually shows a restrictive pattern with an associated gas transfer defect.

Treatment

• For symptomatic patients with moderate or more severe respiratory impairment due to COP, initiation of systemic glucocorticoid therapy is recommended. The usual dose is the equivalent of prednisone 0.75 to 1 mg/kg per day (using ideal body weight) to a maximum of 100 mg/day given as a single oral dose in the morning; most patients respond to a dose of 60 mg per day.

• For patients with rapidly progressive disease or actual/impending respiratory failure, it is suggested to use an initial high-dose glucocorticoid therapy with methylprednisolone 500 to 1000 mg intravenously each day for three to five days rather than a lower oral dose  

• For patients who fail to respond to initial therapy with systemic glucocorticoids or present with fulminant disease, research suggests addition of a second immunosuppressive agent, such as cyclophosphamide or azathioprine .

• Glucocorticoid therapy usually induces clinical improvement and clearing of the opacities on chest imaging of several days to a few weeks. Oral glucocorticoid therapy is gradually tapered as tolerated over 6 to 12 months. Relapses are common upon stopping or reduction of glucocorticoids, often leading to prolonged treatment.

• For patients who are unable to taper glucocorticoids to a level that does not cause intolerable adverse effects, we suggest adding a second immunosuppressive agent, such as azathioprine  
  

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