True primary Sjögren's syndrome in a subset of patients with hepatitis C infection: a model linking chronic infection to chronic sialadenitis.

BACKGROUND: Hepatis C virus infection is presently an exclusion criterion to classify Sjögren's syndrome; however, there are distinct clinicopathologic and biologic similarities between HCV-related and SS-related chronic inflammation of mucosa-associated lymphoid tissue and lymphoproliferation that suggest common pathogenetic pathways.

OBJECTIVES: To determine whether a subset of patients with sicca syndrome and HCV infection may present a true primary SS rather than a distinct clinicobiologic entity.

METHODS: We extensively characterized 20 consecutive patients with positive anti-HCV antibodies and heavy subjective dry eye and/or dry mouth symptoms, plus positive unstimulated sialometry and/or Shirmer's test. We then compared these features with those in HCV-negative primary SS controls (classified according to the latest American-European Consensus Group Classification Criteria for SS).

RESULTS: Of the 20 HCV-positive patients with sicca manifestations, 12 (60%) had positive anti-SSA/SSB antibodies (3/12 by enzyme-linked immunosorbent assay and 6/12 by immunoblot) and/or positive salivary gland biopsy (at least 1 focus/4 mm2), which met the strict classification criteria for SS, as in the case of HCV-negative SS controls. Comparing the HCV-positive SS subset with HCV-negative SS controls showed similar female to male ratio (11/1 vs. 46/4), major salivary gland swelling (17% vs. 26%), positive antinuclear antibodies (75 vs. 94%) and positive rheumatoid factor (58 vs. 52%). Significant differences (P < 0.05) were seen in mean age (69 vs. 56 years), liver disease (50 vs. 2%), lung disease (25 vs. 0%), anti-SSA/SSB positivity (25 vs. 90%), and low C3 or C4 (83 vs. 36%). HCV-positive SS patients exhibited a trend for more frequent chronic gastritis (50 vs. 22%), fibromyalgia (33 vs. 14%), peripheral neuropathy (33 vs. 18%), purpura (33 vs. 19%) and cryoglobulinemia (33 vs. 6%).

CONCLUSIONS: A major subset of HCV-positive patients with definite subjective sicca symptoms and positive objective tests may indeed present a true, though peculiar, subset of SS. There are strict similarities with key clinical, pathologic and immunologic findings of definite HCV-negative SS. Other features appear more characteristic of HCV infection. When also considering that HCV is sialotropic and may be treated, HCV-related chronic sialadenitis represents a unique opportunity to clarify key pathogenetic events occurring in the large majority of HCV-negative SS; and similarities to typical primary SS, rather than differences, should be taken into account.