Background In the widely used American-European Consensus Group (AECG) classification criteria for primary Sjögren's syndrome (pSS), pre-existing lymphoma is one of the exclusion criteria for pSS diagnosis (1). This is in contrast to the American College of Rheumatology (ACR)/Sjögren's International Collaborative Clinical Alliance (SICCA) 2012 classification criteria (2). The rationale and consequences of excluding or not excluding pSS in patients with pre-existing lymphoma have not specifically been described.
Objectives To compare patients with pre-existing lymphoma and a later pSS diagnosis, and patients with pSS and a subsequent lymphoma, derived from a large-population-based cohort of individuals with pSS and lymphoma.
Methods Patients with an International Classification of Diseases (ICD) diagnosis code for “Sjögren's syndrome/sicca syndrome” (SS) and prior or subsequent lymphoma diagnosis were identified by linking the Swedish Patient Register 1964–2007 with the Cancer Register 1990–2007 (n=205). Clinical data and lymphoma tissues were reviewed and the diagnoses evaluated. All 71 patients fulfilling the AECG and/or the proposed ACR-EULAR criteria for pSS (3) with a confirmed lymphoma were included in the study.
Results We identified 11 patients with pre-existing lymphoma, defined as lymphoma diagnosed before (n=4, median time four years to pSS diagnosis) or within six months after pSS diagnosis (n=7, median time three months to lymphoma diagnosis), and 60 pSS patients with subsequent lymphoma.
The pSS characteristics were similar in patients with pre-existing lymphoma and pSS patients with subsequent lymphoma. There were no differences in reported duration of sicca symptoms (median time from sicca onset until pSS diagnosis 5 years in pre-existing lymphoma group vs. 4 years in pSS patients with subsequent lymphoma, p=0.1), sex distribution, median ages at sicca onset, pSS and lymphoma diagnoses, presence of autoantibodies, laboratory findings, overall survival after lymphoma diagnosis, and extraglandular pSS manifestations. However, lymphadenopathy at pSS diagnosis was more common in patients with pre-existing lymphoma (p<0.0001).
There were some differences in lymphoma characteristics. Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) (72% vs. 22%, p<0.002), and lymphoma involvement of the salivary glands (82% vs. 32%, p<0.005) were more common in patients with pre-existing lymphoma than in pSS patients with subsequent lymphoma.
Conclusions This study suggests that pre-existing lymphoma should not be used as a general exclusion criterion for pSS, which may erroneously remain undiagnosed. On the contrary, the combination of sicca symptoms and MALT lymphoma in the salivary glands could instead be a reason for adequate pSS investigation.
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Disclosure of Interest None declared
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