[Clinical study of interstitial lung disease in mixed connective tissue disease]

Mixed connective tissue disease (MCTD) is characterized by a combination of clinical features of progressive systemic sclerosis, systemic lupus erythematosus, rheumatoid arthritis, polymyositis/dermatomyositis, with a high anti-snRNP antibody titer. Respiratory manifestations, such as interstitial lung disease (ILD), are not well-described. Thirteen patients who met the diagnostic criteria for MCTD and showed ILD on high-resolution CT were analysed retrospectively. A restrictive pattern was found in 73% of cases and TLCO abnormalities in 90%. Exercise hypoxemia was observed in nine out of ten cases. The CT-scan pattern was compatible with non-specific interstitial pneumonia in seven cases and with usual interstitial pneumonia in five. Bronchoalveolar lavage showed lymphocytic alveolitis in two patients, neutrophil alveolitis in eight. Fifty percent ILD patients respond to steroids and immunosuppressive drugs. Progressive ILD (six in 13; 46%) compared with non-progressive ILD associated more systemic sclerosis manifestations (p<0.05). Progressive ILD tend to have more frequent pulmonary hypertension, neutrophilic alveolitis and honey combing pattern. MCTD-ILD characteristics are not specific. When systemic sclerosis manifestations are present, MCTD-ILD seems to associate more frequently pulmonary hypertension and progressive ILD.