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Epidemiology
Pathophysiology
Most benign pulmonary disorders are derived from intrinsic or extrinsic injury. Such injury can take the form of cellular and/or humoral immunologic injury triggered by inhaled antigens, infectious agents, or autoimmune processes. Chemical injury from smoking or certain drugs has also been implicated.
Clinical features
Most presenting symptoms include progressive dyspnea and cough. Other symptoms include chest pain, wheezing, and hemoptysis. Physical signs include heavy use of accessory muscles of breathing, cyanosis, and clubbing. Systemic signs of illness seen with some illnesses include fatigue, weight loss, and malaise.
Diagnostics
Most diffuse benign disorders are characterized by plain chest radiography, computed tomography, and open or video-assisted thoracoscopic lung biopsy. Most of these disorders have characteristic radiologic pulmonary parenchymal patterns, adenopathy (e.g., sarcoidosis), and histologic characteristics. Bronchoscopy with transbronchial biopsies/bronchoalveolar lavage, fine-needle aspiration biopsies, and sputum cultures and/or cytologies is also helpful in many cases. Finally, a complete blood count with differential (e.g., eosinophilic processes) and serum chemistries are helpful in some cases.
Treatment
Although treatment recommendations vary with the particular pulmonary process, many are corticosteroid based while others are predicated on removal of an inciting agent (e.g., drug, tobacco smoke).
Outcomes
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Diffuse benign pulmonary disorders cover a broad range of primary lung diseases but may also be associated with systemic disorders. These range from chronic conditions such as idiopathic pulmonary fibrosis (IPF) associated with poor survival to acute disease of hypersensitivity pneumonitis (HP) with usually a good response to treatment. Some of these diseases have unique clinical characteristics while others share similar radiographic changes, symptoms, or pulmonary function abnormalities. Therapy differs for many of the diffuse benign pulmonary diseases, making accurate diagnosis paramount.
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Each of these disorders may occur due to intrinsic or extrinsic injury. For instance, the pneumoconioses are due to the inhalation of damaging foreign material into the lung, while HP is due to an allergic response to foreign material or medications. On the other hand, interstitial lung diseases such as IPF, sarcoidosis, lymphangioleiomyomatosis (LAM), eosinophilic granulomatosis (EG), and the pulmonary disorders associated with collagen vascular disease are believed to be due to intrinsic lung inflammation and injury.
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The benign diffuse lung diseases may also be categorized based on physiologic presentation, particularly the type of change seen by pulmonary function studies. Some of the disorders are associated with an obstructive ventilatory defect (LAM, EG) or restrictive ventilatory defect [IPF, nonspecific interstitial pneumonitis (NSIP), asbestosis], while others may present with combined obstruction and restriction [sarcoid, bronchiolitis obliterans with organizing pneumonia (BOOP)].
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Finally, these diseases may be categorized based on radiographic findings (i.e., diffuse interstitial infiltrates, alveolar infiltrates, cystic lesions, or honeycombing). This chapter reviews the most common benign pulmonary diseases including clinical ...