Anti-GABAB receptor antibodies with autoimmune encephalitis in clear cell renal cell carcinoma: a case report

Encephalitis with anti-γ-aminobutyric acid-B (GABAB) receptor antibodies is an autoimmune encephalitis, which is mainly observed with small-cell lung cancer (SCLC), thymoma, and melanoma. Here, we reported a case of clear cell renal cell carcinoma with the loss of consciousness as a first symptom, which was associated with a rare GABAB receptor antibody limbic encephalitis. A 58-year-old man with a 2-day history of stomachache and unconsciousness. Imaging studies of the head were normal. The abdominal computed tomography revealed a 3.9 cm × 3.8 cm right renal mass with contrast enhanced. Subsequent cerebrospinal fluid antibody testing was positive for anti-GABAB receptor antibodies. After 2 weeks of treatment with nutritional neurologic and immunomodulatory, the symptoms did not improve. Laparoscopic radical nephrectomy was undertaken and subsequently immunotherapy for the patient's treatment. The postoperative pathology was renal cell carcinoma (Clear cell carcinoma, WHO/ISUP grade 3, tumor size 4 cm × 3.5 cm, pT1a). The patient's conditions improved after the surgery. At the 12-month follow-up, computed tomography imaging showed no recurrence, and the patient was living independently. This case was reported to demonstrate that, when patients are presented with GABAB receptor antibody encephalitis, early evaluation of underlying malignancy including renal cell carcinoma and aggressive treatment of primary tumors provide the chances for a better outcome.