Résumé
@#Germ cell tumor is the most prevalent ovarian tumor in young women between 10 and 30 years of age.[1] However, immature teratomas account for only 20% of the malignant ovarian tumors found in the adolescent age group.[2] More uncommon is the occurrence of immature teratoma causing anti‑N‑methyl‑D‑aspartate receptor (Anti‑NMDAR) encephalitis and Guillain‑Barré Syndrome (GBS). This is a case of a 15‑year‑old female, nulligravid, who initially presented sudden behavioral change and symmetrical weakness of both lower and upper extremities with concomitant seizure episodes and with palpable lower abdominal mass. The patient was diagnosed to have GBS and treated with intravenous immunoglobulin causing resolution of neurologic symptoms months after. During the management of GBS, the patient noted increasing abdominal girth. Tumor markers showed elevated alpha‑fetoprotein, CA125, and lactate dehydrogenase. An imaging study revealed predominantly solid ovarian mass hence malignancy was considered. Once the medical condition stabilized, the patient underwent fertility‑sparing surgery with the final histopathologic result of immature teratoma. The aim of this report is to present a case of anti‑NMDAR encephalitis and GBS as paraneoplastic manifestation of immature teratoma.