Refining myositis associated with primary Sjogren's syndrome: data from the prospective cohort ASSESS

Objectives To refine the prevalence, characteristics and response to treatment of myositis in primary SS (pSS). Methods The multicentre prospective Assessment of Systemic Signs and Evolution in Sjogren's Syndrome (ASSESS) cohort of 395 pSS patients with >= 60 months' follow-up was screened by the 2017 EULAR/ACR criteria for myositis. Extra-muscular complications, disease activity and patient-reported scores were analysed. Results Before enrolment and during the 5-year follow-up, myositis was suspected in 38 pSS patients and confirmed in 4 [1.0% (95% CI: 0.40, 2.6)]. Patients with suspected but not confirmed myositis had higher patient-reported scores and more frequent articular and peripheral nervous involvement than others. By contrast, disease duration in patients with confirmed myositis was 3-fold longer than without myositis. Two of the four myositis patients fulfilled criteria for sporadic IBM. Despite receiving three or more lines of treatment, they showed no muscle improvement, which further supported the sporadic IBM diagnosis. The two other patients did not feature characteristics of a myositis subtype, which suggested 'pure' pSS myositis. Steroids plus MTX was then efficient in achieving remission. Conclusions Myositis, frequently suspected, occurs in 1% of pSS patients. Especially when there is resistance to treatment, sporadic IBM should be considered and might be regarded as a late complication of this disease.

Automated summary

The study aimed to investigate the prevalence, characteristics, and treatment response of myositis in primary SS (pSS) patients. Results revealed that approximately 1% of the 395 pSS patients studied had myositis. Patients with suspected myositis had higher patient-reported scores, while those with confirmed myositis had a longer disease duration.