Ovarian teratomas causing anti-N-methyl-D-aspartate receptor encephalitis: a case series from west China.

Background: The incidence of ovarian teratomas (OT) causing anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDARE) is low, and pathological studies of related cases are limited. This study aimed to analyze the clinical data of such patients and to investigate the expression of N-methyl-D-aspartate receptor (NMDAR) and lymphocytes in teratoma tissues to initially investigate the pathogenesis of the disease.

Methods: Clinical data were collected and analyzed. Immunohistochemistry was applied to detect the expression of NMDAR subunits and T/B lymphocytes in 46 patients, including 8 OT patients with encephalitis and 38 regular OT patients. Immunohistochemical expression of NMDARs and T/B lymphocytes in OT tissues in patients with or without anti-NMDARE.

Results: Teratomas causing encephalitis mostly occur in young women. The degree of positive expression of NMDAR, CD4 and CD20 in the encephalitis group differed statistically from the control group (P<0.05). Although there was no linear relationship between the CD4/CD20 expression and the NMDAR expression, clusters of lymphocytes were observed clearly around the squamous epithelium positive for NMDAR expression only in the encephalitis group.

Conclusions: OT leading to encephalitis seems to be associated with high expression of NMDARs in the squamous epithelium of the tissue, where clusters of lymphocytes infiltration is also a unique pathological feature. This is the first multi-case group study about OTs causing anti-NMDARE in southwestern China.