PULMONARY MANIFESTATIONS.

Pulmonary involvement occurs in most patients and is manifested as pleurisy, coughing, dyspnea, abnormal pulmonary function tests, or chest radiographic abnormalities. Pleurisy occurs in over 50% of patients; the most common cause is chest wall pain on local pressure and/or movement. Pleuritis (inflammation of the pleura) also causes pleurisy. It is diagnosed by the presence of a pleural friction rub and/or the radiographic presence of a pleural effusion. Effusions typically have low complement and protein levels, few WBCs (the pleura has mononuclear cells), glucose levels approximating plasma levels (by contrast, they are low in rheumatoid arthritis), and LE cells. Cough usually represents an infection, but pulmonary edema secondary to cardiac or renal failure or fluid overload in a patient receiving corticosteroids should be considered.

Acute lupus pneumonitis occurs in 5 to 12% and is characterized by fever, cough (even hemoptysis), pleurisy, and dyspnea. Radiography shows diffuse acinar infiltrates, especially in the lower lobes. Subsequently, interstitial infiltrates and fibrosis may develop, with pulmonary function abnormalities. The prognosis is poor.

Pulmonary hypertension may complicate SLE but is more frequent with scleroderma or mixed connective tissue disease. Raynaud's phenomenon is common. Late findings include dyspnea, hypoxemia, restricting lung disease, and reduced CO₂diffusing capacity.

The shrinking or vanishing lung syndrome has been described in some patients. It is believed to result from weakening and elevation of the diaphragm (lung fields are radiographically clear).