Background IgG4-related disease and primary Sjögren syndrome (SS) share clinical presentations (sicca features, enlarged exocrine glands) and systemic organ involvement, with histopathological demonstration of IgG4+ infiltrative cells being the key differential feature.
Objectives To compare epidemiological, clinical and analytical features in patients with primary SS and IgG4-related disease.
Methods The GEAS-SS multicenter registry, founded in 2005, includes 921 consecutive Spanish patients fulfilling the 2002 primary SS classification criteria. IgG4-related disease patients fulfilling the 2012 criteria (Umehara et al) were collected by systematic review (2000-2013, 23 studies including 662 patients).
Results Primary SS patients had a similar mean age at diagnosis (54 vs 60 years, p>0.05) and were more frequently female (94% vs 40%, p<0.001) than IgG4-related disease patients. Sicca symptoms were more frequent in primary SS (oral dryness 95 vs 32%, p<0.001, ocular dryness 95 vs 24%, p<0.001). Globally, glandular enlargement was higher in IgG4-related disease patients (75% vs 35%, p>0.001), with a clear predominance of submaxillar (71% vs 15%, p<0.001) and lachrymal gland (44% vs 5%, p<0.001) involvement, while parotid gland enlargement was more frequent (34% vs 27%, p=0.04) in primary SS. Systemic involvement differed clearly, with a higher frequency of skin (15% vs 3%), joint (13% vs 0%), liver (15% vs 2%) and peripheral nerve (10% vs 1%) involvement in primary SS patients (p<0.001 for all comparisons) and a higher frequency of pancreatic (23% vs 2%), renal (18% vs 4%), retroperitoneal (13% vs 0%), biliary tract (10% vs 0%) involvement and adenopathies (44% vs 10%) in IgG4-related disease patients (all comparisons p<0.001). Primary SS patients had a higher frequency of the main immunological markers (ANA 90% vs 28%, RF 57% vs 24%, Ro/SS-A 73% vs 2.5%, La/SS-B 46% vs 0%, all comparisons p<0.001) except hypocomplementemia (12% vs 46%, p<0.001, while 91.2% of IgG4-related disease patients and only 4.7% of primary SS patients had raised serum IgG4 levels (>135 mg/dL) (p<0.001), with a mean of 789,07 mg/dL vs 42,12 mg/dL (p<0.001), and a % ratio IgG4/total IgG of 34.5% vs 2.1% (p<0.001). Mean IgG4+ cells per HPF in available histopathological samples were 104 (range 13-229) in IgG4-related disease patients and <5 in primary SS patients.
Conclusions Although IgG4-related disease and primary SS share similar clinical presentations, significant differences in epidemiological features, organ-specific involvement and immunological profiles may aid early clinical diagnosis, with raised serum IgG4 levels and tissular infiltration by IgG4+ cells being key differentiating features. A clinical score including the parameters identified could aid differentiation between IgG4-related disease and primary SS in daily paractice.
Disclosure of Interest : None declared