Anti-Ro52/TRIM21 autoantibodies predict Sjögren's syndrome in patients with primary biliary cholangitis

Sjögren's syndrome is a common comorbidity in patients with primary biliary cholangitis (PBC). Anti-Ro52 autoantibodies against the protein TRIM21 are often seen in Sjögren's syndrome. TRIM21 consists of four domains (PRY/SPRY, Coiled-Coil, B-box, and RING domain), each with a specific function. We hypothesized that patients with PBC and concomitant autoantibodies against TRIM21 had a higher risk of developing Sjögren's syndrome.

Using ELISA, we analyzed plasma from 236 Danish patients with PBC. Binomial regression assessed the risk rates between demographics, serologic variables, PBC-40 results, and autoantibody positivity.

Forty patients (16.9%) tested positive for anti-Ro52 autoantibodies, with 23 (9.7%) samples positive against Coiled-Coil, 12 against PRY/SPRY (5.1%), and 10 against RING (4.2%). Increased IgG plasma levels, reports of dry mouth, and a diagnosis of Sjögren's syndrome increased the risk of both anti-Ro52 and all domain autoantibodies. In the anti-Ro52 positive subgroup, no less than 14 undiagnosed patients met the criteria for Sjögren's syndrome.

We observed a 16.9% positivity of anti-Ro52 autoantibodies and an association between having these autoantibodies and elevated IgG, the symptom dry mouth, and having Sjögren's syndrome. Furthermore, we found a sizable undiagnosed group of Sjögren's patients in the anti-Ro52 positive subgroup. Our results suggest that Sjögren's patients are underdiagnosed in patients with PBC. We propose that patients with PBC be tested for anti-Ro52 autoantibodies and, if positive, referred for rheumatological examination.