From the Guidelines
Obliterative bronchiolitis is a rare and progressive lung disease characterized by inflammation and scarring of the small airways (bronchioles), leading to their narrowing and obstruction, as described in the British Thoracic Society guideline for the use of long-term macrolides in adults with respiratory disease 1. This condition, also known as bronchiolitis obliterans, results in irreversible airflow limitation and respiratory symptoms. It typically develops following lung transplantation, hematopoietic stem cell transplantation, or exposure to certain toxins and chemicals like diacetyl (found in artificial butter flavoring) 1. Patients experience progressive shortness of breath, dry cough, wheezing, and fatigue that worsen over time.
Diagnosis and Management
The diagnosis of obliterative bronchiolitis requires a comprehensive medical history, physical examination, physiologic testing, and radiographic studies, as outlined in the ACCP evidence-based clinical practice guidelines 1. Treatment focuses on slowing disease progression rather than cure, using immunosuppressants like corticosteroids, calcineurin inhibitors, and antifibrotics in some cases.
- Bronchodilators such as long-acting beta-agonists and anticholinergics may provide symptomatic relief.
- Oxygen therapy becomes necessary as the disease advances.
- Prevention is crucial, particularly in transplant recipients, through appropriate immunosuppression regimens and avoiding environmental exposures, as recommended in the international ISHLT/ATS/ERS clinical practice guideline 1.
Key Recommendations
- For lung transplant recipients who develop a decline in FEV1 consistent with the onset of BOS, a trial of azithromycin is suggested 1.
- The use of long-term, high-dose corticosteroids is not recommended for lung transplant recipients who develop BOS 1.
- Switching from cyclosporine to tacrolimus may be considered for lung transplant recipients who develop BOS while receiving chronic immunosuppression with a regimen that includes cyclosporine 1.
The disease process involves immune-mediated inflammation triggering fibroblast proliferation and collagen deposition, ultimately causing irreversible airway obstruction and lung function decline.
From the Research
Definition and Characteristics of Obliterative Bronchiolitis
- Obliterative bronchiolitis (OB) is a rare fibrotic disorder involving terminal and respiratory bronchioles, also known as constrictive bronchiolitis 2.
- It is characterized by progressive airflow obstruction, absence of parenchymal infiltrates on chest radiographs, and a mosaic pattern of perfusion on high-resolution computed tomographic scan 2, 3.
- The disease often results in poor responsiveness to therapy and high mortality rates 2.
Causes and Risk Factors
- Most cases of OB occur in the context of a specific risk factor, such as lung transplant recipients with chronic allograft rejection or hematopoietic stem cell transplant (HSCT) recipients with graft versus host disease (GVHD) 2, 3.
- Other causes of OB include connective tissue disease, lower respiratory tract infections, inhalation injury, exposure to toxic fumes or pollutants, occupational exposures, drug reactions, and consumption of uncooked leaves of Sauropus androgynus 2.
- When no cause is identified, the term cryptogenic obliterative bronchiolitis is used 2.
Diagnosis and Management
- Diagnosis of OB is based on clinical, radiographic, and histological features, although lung biopsy and histopathology remain the gold standard approaches to confirm the disease 2, 4, 5.
- Management of OB requires a multidisciplinary approach and care in specialized centers, with augmentation of immunosuppression occasionally effective in slowing or reversing the progression of disease 3, 6.
- Long-term azithromycin treatment has been shown to improve pulmonary function in some patients with established OB 6.