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Clin Exp Rheumatol. 2015 Jul-Aug;33(4):457-64. Epub 2015 Jun 19.

Myositis in primary Sjögren's syndrome: data from a multicentre cohort.

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Department of Internal Medicine and Medical Specialties, Rheumatology Unit, Sapienza University of Rome, Italy.
Department of Radiological Sciences, Oncology ed Anatomo-Pathology, Sapienza University of Rome, Italy.
Rheumatology Clinic, DSMB, University of Udine, Italy.
Rheumatology Unit, Department of Clinical and Experimental Medicine, University of Perugia, Italy.
Rheumatology Clinic, University of L'Aquila, Italy.
Rheumatology Unit, University of Pisa, Italy.



In primary Sjögren's syndrome (pSS), muscle pain and/or muscular weakness is relatively frequent while myositis has been reported in 3% of patients. The aim of this study was to describe the prevalence of myositis in a multicentre Italian pSS cohort and to address the clinical manifestations, histological findings and therapeutic strategies.


Clinical, serological and therapeutic data from a pSS cohort of patients were retrospectively collected. According to Bohan and Peter's criteria, inflammatory myopathy (IM) was suspected in case of muscular weakness associated with increased creatine-phosphokinase (CPK) or abnormal electromyography (EMG). When performed, muscle biopsies were analysed.


In a cohort of 1320 patients, 17 (1.28%) presented muscular weakness [in some cases myalgias (7/17, 41.1%)], accompanied by increased CPK [13/17, (76.4%)] and/or abnormal EMG [13/14, (92.8%)]. Ten out of 17 (58.8%) fulfilled at least three diagnostic criteria for IM. Muscular biopsy was performed in 13/17 (76.4%) cases with histologically confirmed myositis in 6/13 (46.1%) (1"IBM-like"-5"PM-like"). In two "PM-like" cases, several fibres showed a decreased histochemical cytochrome C oxidase (COX) stain. Two biopsies tested "negative", four showed "non-specific" findings. All patients were treated with corticosteroids followed by different DMARDs.


Our retrospective analysis shows a prevalence of myositis in pSS lower than previously reported, mainly appearing as an overlapping syndrome. Histological findings confirm the possible presence of an IBM or of a myopathy more similar to PM with a decreased COX activity. Classical immunosuppressants are effective although in most difficult cases IVIg or RTX may be used with benefit.

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