Sjögren's syndrome associated with systemic lupus erythematosus: clinical and laboratory profiles and comparison with primary Sjögren's syndrome.

OBJECTIVE: To address the clinical, serologic, pathologic, and immunogenetic features of sicca syndrome that occurs in systemic lupus erythematosus (SLE), as well as its similarities to, and differences from, sicca syndrome that occurs in primary Sjögren's syndrome (SS).
METHODS: A cohort of 283 consecutive unselected SLE patients was evaluated for the presence of associated SS using the American-European classification criteria. Clinical and laboratory parameters in SLE patients with SS (SLE-SS) were compared with those in SLE patients without SS (SLE-no SS) and with a group of 86 unselected patients with primary SS.
RESULTS: SS was identified in 26 SLE patients (9.2%); the SS preceded the development of lupus in 18 of them (69.2%). Compared with the SLE-no SS group, patients with SLE-SS were significantly older, had a higher frequency of Raynaud's phenomenon, anti-Ro/SSA, anti-La/SSB, and rheumatoid factor, but had a significantly lower frequency of renal involvement, lymphadenopathy, and thrombocytopenia. Compared with the primary SS group, SLE-SS patients displayed a clinically similar sicca syndrome, but were significantly younger and had an increased frequency of perivascular infiltrates in the salivary glands associated with anticardiolipin antibodies in the serum. SLE-SS patients had a high frequency of the DRB1*0301 allele. This HLA profile distinguished the SLE-SS group from the SLE-no SS group, who had an increased frequency of DRB1*1501 and DQB1*0602 alleles, but was similar to the HLA profile of the primary SS group, who had an increased frequency of DRB1*0301.
CONCLUSION: SLE-SS appears to constitute a subgroup of patients with distinct clinical, serologic, pathologic, and immunogenetic features, in whom SS is expressed as an overlapping entity and is largely similar to primary SS.