CLINICAL MANIFESTATIONS



The spectrum of clinical presentation in this group of disorders is as varied as the conditions themselves. The majority of patients present with an insidious onset of dyspnea, exercise limitation, and a dry, nonproductive cough. Certain historical features may suggest a specific diagnosis as detailed in the discussion of each entity. Exami­nation of the chest characteristically reveals mid to late inspiratory crackles and tachypnea. Phys­ical findings of pulmonary hypertension, cor pul­monale, and cyanosis are usually late findings. Evidence of extrathoracic disease is valuable in suggesting a specific diagnosis, such as the skin lesions of sarcoidosis or the arthritis of a collagen-vascular disease. The chest x-ray may confirm the presence of diffuse infiltrative disease but is rarely diagnostic on its own.

The physiological consequences depend on the proportion of lung involved and the speed with which the infiltration develops. As fibrosis re­places normal lung structures, there is a decrease in all lung volumes, a fall in lung compliance, and a decline in the diffusing capacity. The loss of alveolar space and airway abnormalities produce ventilation-perfusion inequality, but hypoxemia is usually mild until the disease progresses to a significant degree and hypercapriia is uncommon.

A specific diagnosis, when not clear from the presentation, depends on lung biopsy findings. In certain diseases, such as sarcoidosis, sufficient tissue can be obtained using a fiberoptic bron­choscope and a transbronchial biopsy, but this may be insufficient in others, such as idiopathic pulmonary fibrosis, and an open lung biopsy may be required.