Bilateral exudative pleuritis, an unusual pulmonary onset of mixed connective tissue disease

In mixed connective tissue disease (MCTD) pulmonary involvement has been reported. In most patients diffuse interstitial pulmonary abnormalities are present. We describe an unusual pulmonary onset of MCTD in an 18-year-old woman. She presented with a bilateral pleural exudate containing many granulocytes (95%) and only a few monocytes (5%). High titers of antinuclear antibodies were found. One week after hospitalization, an erythema on both hands and forearms developed. Skin biopsy demonstrated discrete IgM-C3 depositions along the basal membrane of the epidermis, antinuclear antibodies in the nuclei of the keratocytes in the dermis and granular depositions of IgM in the blood vessel walls of the upper dermis. Lung function tests improved without corticosteroid treatment and diffusing capacity remained normal.