The objective was to study the clinical and laboratory characteristics of mixed connective tissue disease (MCTD). It was a cross-sectional descriptive study. There were 45 patients who were diagnosed as having mixed connective tissue disease from 7/2010 - 7/2012 at the Allergy and Clinical Immunology Center in Bach Mai Hospital, MCTD was diagnosised by using Alarcon-Segovia (1987) criteria. Arthralgia was the most obvious symptom that was seen, 100 percent patients
following by Raynaud syndrome, 93.3 percent. The most common symptoms were muscle pain (86.7 percent), loss of skin wrinkles (82.2 percent), difficulty breathing and chest tightness (88. 9 percent) and muscle damage, 71.1 percent. In the study, the high concentration of autoimmune antibodies was seen in most patients, ANA (Antinuclear antibodies) was 97.8 percent
anti-RNP70 (Anti Ribonucleotidprotein 70) was 100 percent. Interstitial pneumonia and pulmonary artery pressure was seen in many patients. In conclusion, MCTD had overlapping clinical lesions of other autoimmune diseapes
had high titer ANA
had high titer anti-RNP70. There are 64.5 percent patients with interstitial lung injury and PHA 89.3 percent of patients received an echocardiogram.