Systemic disorders that may have a component of airflow limitation suggest COPD; they include HIV infection Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more , abuse of IV drugs (particularly cocaine and amphetamines), sarcoidosis Sarcoidosis Sarcoidosis is an inflammatory disorder resulting in noncaseating granulomas in one or more organs and tissues; etiology is unknown. The lungs and lymphatic system are most often affected, but... read more , Sjögren syndrome Sjögren Syndrome Sjögren syndrome is a relatively common chronic, autoimmune, systemic, inflammatory disorder of unknown cause. It is characterized by dryness of the mouth, eyes, and other mucous membranes ... read more , bronchiolitis obliterans Work-Related Asthma Work-related asthma includes both occupational asthma and work-exacerbated asthma. Occupational asthma is new-onset asthma that is caused by exposure to either allergens or irritants in the... read more , lymphangioleiomyomatosis Lymphangioleiomyomatosis Lymphangioleiomyomatosis (LAM) is an indolent, progressive growth of smooth muscle cells throughout the lungs, pulmonary blood vessels, lymphatics, and pleurae. It is rare and occurs in young... read more , and eosinophilic granuloma. COPD can be differentiated from interstitial lung diseases Overview of Interstitial Lung Disease Interstitial lung diseases are a heterogeneous group of disorders characterized by alveolar septal thickening, fibroblast proliferation, collagen deposition, and, if the process remains unchecked... read more by chest imaging, which shows increased interstitial markings in interstitial lung disease, and pulmonary function testing, which shows a restrictive ventilatory defect rather than an obstructive ventilatory defect. In some patients, COPD and interstitial lung disease coexist (combined pulmonary fibrosis and emphysema [CPFE]) in which lung volumes are relatively preserved, but gas exchange is severely impaired.