Hyperviscosity in primary Sjögren's syndrome: clinical implications.

Aim: Increased serum viscosity is recognized in primary Sjögren's syndrome (pSS); however, a classic hyperviscosity syndrome (HVS) is rare. We compared the clinical and serological profile among three groups of pSS patients: (i) with HVS; (ii) with high serum viscosity (≥ 1.9 cP [centipoises]) but without HVS; and (iii) with normal viscosity (< 1.9 cP).

Methods: We identified four pSS patients with HVS and retrospectively assessed their clinical/serological features. We included as controls 62 pSS patients and registered their clinical features. We also measured the serum viscosity, C3, C4, immunoglobulins and evaluated the European League Against Rheumatism SS Disease Activity Index (ESSDAI) score at the last visit. We used χ , Mann-Whitney U-tests and logistic regression analysis.

Results: Patients were predominantly female (95%), mean age 54 ± 14.2 years, median disease duration 9 years. All the HVS cases were diagnosed concomitantly with the onset of SS and had higher titers of immunoglobulin G (IgG), IgM, IgA and a higher prevalence of vasculitis, neutropenia, lymphopenia and splenomegaly. At the multivariate analysis, the variables vasculitis odds ratio (OR) 14.8 (95% CI 1.3-99, P = 0.02) and splenomegaly OR 25.3 (95% CI 1.68-380, P = 0.01) remained associated with HSV. Viscosity levels correlated with rheumatoid factor titers. Thirty (48.3%) patients had high viscosity but without HSV; this group had higher median ESSDAI scores and more vasculitis than patients with normal viscosity.

Conclusion: High viscosity was present in almost half of the patients and was associated with vasculitis and higher activity scores. Conversely, HVS was infrequent and was associated with vasculitis and splenomegaly. It seems that both conditions have different physiopathological, clinical and treatment implications.