Acute Encephalitis in Primary Sjögren's Syndrome: A Case Report and Literature Review.

Acute encephalitis is an extremely rare condition in primary Sjogren's syndrome (pSS), and its characteristics and prognosis remain unclear. Here we report the case of pSS presented with acute encephalitis. She was admitted to our hospital for acute disturbance of consciousness. Acute encephalitis was diagnosed based on the results for cerebrospinal fluid test (the increase of leukocyte counts, protein, and interleukin-6 level), magnetic resonance imaging (a high signal intensity of the white matter around lateral ventricle on T2 FLAIR images), and single photon emission computed tomography with 99mTc (hypoperfusion in the bilateral cerebrum with frontal lobe predominance). The infectious etiologies and underlying malignancies were excluded. Serum anti-SSA/Ro antibody was positive with extremely high titer, whereas anti-dsDNA, anti-Sm, anti-ribosomal P, anti-RNP, and anti-phospholipid antibodies were all negative. Anti-NAE, anti-NMDAR, and anti-ribosomal P antibodies in cerebrospinal fluid were absent. The biopsy specimen of her labial salivary gland revealed a focal lymphocytic sialadenitis with a score of grade 4 in Greenspan grade. She also developed diffuse alveolar hemorrhage during the clinical course. She was diagnosed with pSS complicated with acute encephalitis followed by diffuse alveolar hemorrhage and successfully treated with pulse steroids, high dose of prednisolone and intravenous cyclophosphamide. Our present case and literature review suggest that acute encephalitis associated with pSS can be treatable with the immunosuppressive therapy, and thus, early recognition and treatment initiation are important for this life-threatening condition. Thus, pSS should be included in the differential diagnosis of unexplained encephalitis. Notably, our case characteristically showed diffuse alveolar hemorrhage, adding the new insight in the pathogenesis of acute encephalitis associated with pSS that capillaritis might be the underlying cause of this condition. (272 words).