Sjögren's syndrome-associated myositis with germinal centre-like structures.

Objective: Muscular impairment is a rare systemic manifestation of SS that is rarely described in the literature and classically non-specific, both clinically and histologically. We reviewed the cases of 4 patients with primary SS presenting with myositis and a common histologic pattern on muscular biopsy with germinal centre-like structures resembling that which occurs in salivary glands.

Methods: We analysed the data files of patients with SS who had muscular manifestations and underwent a muscular biopsy. Among 23 patients with SS who had muscle biopsies, 13 had non-specific myositis and 10 (4 primary and 6 secondary SS) had a common histologic pattern consisting of germinal centre-like structures. We analysed the data files of the 4 patients with primary SS presenting with myositis with muscular germinal-centre like structures.

Results: The 4 patients had an unspecific clinical presentation, with myalgias, muscular weakness and normal or elevated values of CPK. In the four patients, SS-associated myositis had common histologic characteristics, with endomysial and perimysial inflammatory infiltrate. The cellular infiltrate was composed predominantly of CD4+ T lymphocytes and B lymphocytes. The B and T CD4+ cells infiltrates may gather into masses, even forming lymphoid follicles. Three patients were treated with corticosteroids and/or hydroxychloroquine with improvement of myositis and 1 patient was lost to follow-up.

Conclusions: We describe four patients with a common histologic appearance of myositis with lymphoid follicles associated with primary SS. The clinical presentation was non-specific and non-severe, with favorable outcome with corticosteroids and/or hydroxycholoroquine. The discovery of this particular histologic appearance in a muscle biopsy independent of the final diagnosis should indicate the possibility of SS.