Idiopathic inflammatory myopathy associated with Sjögren’s disease : features of a distinct clinical entity

Background: Idiopathic inflammatory myopathies (IIM) and Sjögren’s disease
(SjD) may coexist, but data on their combined presentation and treatment
response remain limited.
Methods: We retrospectively analyzed 23 patients with biopsy-confirmed IIM
and coexisting SjD, compared to 24 age- and sex-matched IIM controls without
SjD. Clinical, electrophysiological, and immunological data, as well as treatments
and outcomes, were assessed. Outcome assessment included EULAR Sjögren’s
Syndrome Disease Activity Index (ESSDAI) and the ACR/EULAR Myositis Response
Criteria for adult polymyositis and dermatomyositis.
Results: Among IIM-SjD patients, 39% had inclusion body myositis (IBM), 61% had
poly- or dermatomyositis. Compared to controls, asymmetric muscle weakness
(78%, p=0.0012), non-muscular manifestations (52%, p=0.0035), and more
immunosuppressive therapies (median 3; p=0.0253), including more frequent
anti-CD20 use (30%, p=0.0039) were found in IIM-SjD. After a median follow-up
of 80 months, patients showed better outcomes (lower ESSDAI and higher ACR/
EULAR response scores; p=0.0031 and p=0.0083). IBM was a strong predictor of
higher ESSDAI scores at follow-up (p=0.014).
Conclusions: The study suggests that IIM-SjD is characterized by more
asymmetric muscle weakness and extramuscular involvement. Enhanced
immunosuppression led to better outcomes in patients with poly- or
dermatomyositis, while IBM was linked to higher disease activity. Further
research is needed to clarify underlying mechanisms.