How causes connective tissue diseases? CTD are characterized as a group by the presence of overactivity of the immune system that results in the production of extra antibodies into the circulation rheumatoid factors(rf), antinuclear autobodies(ana), anti-SSa anti-SSb anti-Smith anti-Jo1 anti-RNP ani-CCP(Cyclic Citrullinated Peptide) ANCA (anti-neutrophil cytoplasmic antibody ) and so on CTD are characterized as a group by the presence of overactivity of the immune system that results in the production of extra antibodies into the circulation. rheumatoid factors (RF), antinuclear autobodies (ANA), anti-SSA，anti-SSB, anti-Smith , anti-Jo1, anti-RNP, ani-CCP (Cyclic Citrullinated Peptide), ANCA (anti-neutrophil cytoplasmic antibody ), and so on. How causes connective tissue diseases?