Background: Autoimmune connective tissue diseases (ACTDs) are the diseases that affect many organs in the body. The presence of autoantibodies is considered as the gold standard in diagnosis of autoimmune connective tissue diseases. Objective: To determine the type of autoantibodies in sera of patients with autoimmune connective tissue diseases in Vietnam National Hospital of Dermatology and Venereology. Methods: A total of 40 patients with autoimmune connective tissue diseases treated atVietnam National Hospital of Dermatology and Venereology were enrolled in the study. The authors used protein immunoprecipitation (lPP) method, which was approved by the Kanazawa University Graduate School of Medical Science and Kanazawa University Hospital to determine the type of autoantibodies in sera of patients. Results: The antibodies detected in SLE group were anti- U1 RNP antibodies (51.35 percent), anti-SSA (32.43 percent), anti Smith (5.41 percent) and anti-SSB (2.70 percent)
in scleroderma group were anti- Scl 70 (57.14 percent), anti-U1 RNP, anti-SSA, anti-RNAP 1/111/11 (14.29 percent)
in dermatomyositis group were anti p155/140, anti-CADM-140, anti MJ (25 percent)
in overlap group were anti Smith, U1 RNP and anti -SSA. Conclusion: Protein IPP is available to detect many types of autoantibodies that is not detected by other methods.