Lupus pneumonitis may present as either an acute or a chronic illness. Lupus pneumonitis is rarer than pulmonary hemorrhage, with an incidence ranging from 1.5 to 9 per cent. In several reported cases, lupus pneumonitis has been the first manifestation of the disease. The pathophysiology of both acute and chronic lupus pneumonitis involves deposition of immune complexes in the blood vessels and alveolar walls with or without associated vasculitis. Acute lupus pneumonitis is reported to occur more frequently during the immediate postpartum period in women who have SLE. It is usually accompanied by other manifestations of SLE. It mimics acute lung infection so that an infectious etiology for respiratory illness should be excluded. Acute lupus pneumonitis is characterized by the acute onset of dyspnea, high fever, and cough, with occasional hemoptysis. Physical findings are minimal unless hypoxia is severe enough to cause cyanosis. A slightly elevated leukocyte count, increased erythrocyte sedimentation rate, and significant hypoxemia may be present. The chest radiograph may exhibit unilateral or bilateral localized, diffuse, or patchy lung infiltrates, predominantly in the lower lung zones, with small pleural effusions. Histologically, acute lupus pneumonitis reveals non-specific changes that may include interstitial pneumonia, edema, and arteriolar thrombi. Vasculitis of major vessels is uncommon. Culture of lung tissue for pathogenic organisms is usually negative. A lung biopsy is rarely indicated and is not usually helpful. Since pulmonary infections and other non-specific pulmonary parenchymal abnormalities are more common in these patients, a diagnostic bronchoalveolar lavage should be performed to exclude an infectious process. The diagnosis of lupus pneumonitis is one of exclusion.
The chronic form of lupus pneumonitis is characterized by diffuse interstitial lung disease. Clinical findings include dyspnea on exertion, non-productive cough, and basal crackles.
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