To compare features of SS in RA with primary SS and RA without SS.
Patients hospitalized between January 2007 and December 2010 were retrospectively studied. Seventy-four cases of overlap RA and SS (RA/SS) among 509 cases of RA were identified. Cases of SS (n = 187) detected during the same period acted as controls.
Among those with RA/SS, there were 46 cases of RA-onset SS and 12 cases of SS-onset RA. Sixteen patients had simultaneous-onset RA and SS. Compared with RA without SS, RA/SS patients had more severe arthritis; a higher incidence of haematological abnormality, fever and rash; and a higher frequency of RF, ANAs and anti-SSA and anti-SSB antibodies (P < 0.05). Compared with primary SS, RA/SS patients were older, had more severe arthritis, anaemia and lung involvement; a lower incidence of fever, rash, leucopenia, thrombocytopenia and hyperthyroidism; and a higher frequency of RF, anti-keratin antibody, anti-perinuclear factor and anti-cyclic citrullinated antibodies (P < 0.05). Compared with RA and primary SS, RA/SS patients had higher disease activity scores of both RA and SS.
RA/SS patients have distinctive features, with more complications and systemic involvement. In addition, disease activity is higher in RA/SS.