Several classes of medications cause the bronchiolitis obliterans organizing pneumonia (BOOP) reaction, including the antimicrobials, anticancer agents,. cardiac agents, and anti-inflammatory agents. The BOOP reaction represents an inflammatory response of the lung, and, therefore, is generally reversible by drug cessation or corticosteroid therapy. Organizing pneumonia is a general term that includes BOOP This article includes a review of the clinical findings, radiographic abnormalities, physiologic findings, and management of drug-induced BOOP.

Reports of the characterization and understanding of bronchiolitis obliterans organizing pneumonia (BOOP) have continued at an accelerated rate for several years. The radiographic and high-resolution CT features of BOOP continue to be documented. There have been new insights into the pathogenesis of BOOP. An animal model has been developed. Video-assisted thoracoscopic biopsy has become a standard for confirming the diagnosis. Childhood BOOP has been described in several reports. Idiopathic BOOP continues to be the most common type; however, a variety of clinical settings such as inhalation of mold spores and associated disorders such as renal transplantation continue to be described. This paper provides an update of advances in the pathogenesis, radiographic features, clinical course, and categorization of the heterogeneity of BOOP.

Bronchiolar lesions are becoming increasingly recognized as an important cause of airflow obstruction. For this reason, it is helpful to have an update of the current clinical, radiographic, and immunologic perspective. Among the bronchiolar airflow disorders, diffuse panbronchiolitis is related to HLA antigen Bw54, and low-dose, long-term erythromycin appears to be effective therapy. Bronchiolitis obliterans can be classified histologically as constrictive bronchiolitis and as proliferative bronchiolitis obliterans. Idiopathic, postfume, postinfectious, and connective tissue disease bronchiolitis obliterans continue to be rare and often have a poor prognosis. Bronchiolitis obliterans associated with lung transplantation is undergoing intensive investigation with regard to pathogenesis, immunologic study, early detection, and treatment. The lesion appears to be a form of chronic organ rejection. The recognition of the distinctive differences among the bronchiolar airflow disorders by clinicians and clinical investigators is essential for improved patient care, for a greater understanding of the pathogenesis of the disorder, and for development of new therapeutic advances.

The workplace has been a source of lung injury for centuries, yet awareness of the types of injuries has varied over time. Because of distinctive differences among the occupational lung disorders, a continual update of the clinical findings, dose response data, physiologic characteristics, and radiographic findings is needed. The radiologist plays a key role for the evaluation of miners, foundry or factory workers exposed to mineral dusts, and of workers exposed to the "biologic" dusts, infectious agents, cancer causing agents, and chemicals causing interstitial lung diseases. This overview includes a discussion of classification systems, criteria for diagnosis of occupational lung diseases, the pulmonary clinician's evaluation, and important aspects of specific disorders and concludes with a discussion of pulmonary disability determination.

There are several bronchiolar diseases with different pathologic and clinical findings. Idiopathic BOOP is a distinct entity consisting of a flu-like illness, late inspiratory crackles, patchy infiltrates roentgenographically, and physiologically decreased vital capacity and diffusing capacity. Response to corticosteroid therapy is good and relapse does not occur if sufficient therapy is given. Bronchiolitis obliterans organizing pneumonia is an appropriate description of this entity. The term is specific because it includes bronchioles and alveoli and excludes disorders involving only alveoli such as organizing pneumonitis or organizing diffuse alveolar damage. The term is general enough to include a sufficient number of patients with a homogenous disorder. Furthermore, the entity can be described to clinicians and pathologists throughout the world in such a fashion that patient care and research can be standardized. Researchers from different centers studying the cause or utilizing treatment protocols are able to discuss a single BOOP entity rather than comparing results of a heterogeneous group of many different types of interstitial lung disorders. This will lead to breakthroughs in discovery of etiologic causes and new effective therapeutic regimens.

Presentation of CaseA 68-year-old man was admitted to the hospital because of recurrent hemoptysis.There was a history of hemoptysis 30 years earlier, followed by resection of a hamartoma of the right upper lobe. Twenty-five years before admission an x-ray film of the chest was said to show evidence of pulmonary tuberculosis. Isoniazid and aminosalicylic acid were given for a "few weeks"; no further details were available.The patient was then well until four years before entry, when he began to have bouts of "bronchitis" with bronchospasm and hemoptysis each winter. The episodes became worse during each successive winter, . . .

Bronchiolitis obliterans is a nonspecific pathologic lesion seen after fume inhalation and infections, which is associated with connective tissue disorders and is a complication of organ transplantation. Bronchiolitis obliterans with organizing pneumonia is also associated with the connective tissue disorders but is usually idiopathic and has better prognosis with corticosteroid therapy. Bone marrow-related obliterative bronchiolitis is limited to patients who develop chronic graft-versus-host disease. Symptoms begin with cough in 3 to 6 months and progress to dyspnea and severe airflow obstruction. The roentgenogram is normal or shows hyperinflation. Prognosis is poor and most patients develop disabling irreversible airflow obstruction. Bronchiolitis obliterans is the most important clinical complication in heart-lung transplant recipients. It is not preceded by typical features of chronic graft-versus-host disease, but has the same clinical course of dyspnea, airflow obstruction, and poor response to therapy. Bronchiolitis obliterans in transplant recipients may represent a form of allograft rejection.

Abnormality of gas exchange is best evaluated by the exercise alveolar-arterial oxygen pressure difference, P(A-a)O2. We studied the P(A-a)O2 in 168 patients with sarcoidosis, desquamative interstitial pneumonia (DIP), usual interstitial pneumonia (UIP), berylliosis, and asbestosis who were seen for clinical and disability consultations. The increase of P(A-a)O2 with exercise was greatest in UIP (mean 16 mm Hg), least in sarcoidosis (mean 1 mm Hg), and intermediate in DIP, berylliosis, and asbestosis (means 9, 9, and 7 mm Hg, respectively). The increase was best predicted by the single breath diffusing capacity (Dsb), and it occurred in patients with sarcoidosis and DIP if the Dsb was less than 50 percent predicted and in patients with the other diseases if the Dsb was less than 70 percent predicted. However, the magnitude of the increase could not be predicted from resting tests, even when multilinear regression equations were used. We conclude that for clinical evaluation of patients with interstitial lung disease, the exercise test with arterial blood gas measurement adds important information if the Dsb is less than 70 percent predicted. For disability evaluation, the invasive exercise study may be helpful when there is a wide discrepancy between clinical findings and resting physiologic studies.