目的:首次报道1例伴顽固性低钠血症的抗 y-氨基丁酸B 受体(gamma-aminobutyric acid B receptor,GABA_BR)抗体相关脑炎合并小细胞肺癌患者,旨在进一步认识其临床特征、可能的发生机制、诊治方法以及预后。

方法:报道1例伴顽固性低钠血症的抗 GABA_BR 抗体相关脑炎合并小细胞肺癌患者的临床表现、辅助检查结果、诊疗经过以及预后,并结合相关文献复习,分析可能的发生机制。

结果:患者为老年女性,因“发作性意识不清伴四肢抽搐"就诊,并且很快进展为癫痫持续状态,伴有精神异常和认知障碍。血和脑脊液抗 GABA_BR 抗体阳性,合并顽固性低钠血症。头颅 MRI 检查未见明显异常。PET-CT检查显示，左侧肺门及左肺下叶结节及团块影,伴¹⁸F-氟代脱氧葡萄糖(¹⁸F-fluorodeoxyglucose,¹⁸F-FDG)代谢异常增高,考虑恶性病变可能。经皮肺穿刺活检诊断为左肺小细胞癌伴纵膈淋巴结转移。给断为左肺小细胞癌伴纵膈淋巴结转移。给予糖皮质激素冲击治疗、静脉滴注丙种球蛋白、小细胞肺癌化疗和放疗以及针对癫痫发作、精神症状和低钠血症的对症治疗后,患者的癫痫发作、精神症状和认知障碍均有所缓解,但低钠血症仍无法纠正,同时肺部肿瘤病灶逐渐增大。后续随访发现患者可能发生小细胞肺癌脑转移。

结论:抗 GABA_BR抗体相关脑炎伴顽固性低钠血症可能与自身免疫或小细胞肺癌所致的抗利尿激素异常分泌相关,但对其发生机制尚待进一步阐明。

Objective: This is the first report of a case of anti-gamma-aminobutyric acid B receptor(GABA_BR)antibody-associated encephalitis with refractory hyponatremia and small-cell lung cancer, in order to further understand the clinical features, possible pathogenesis diagnosis and treatment, and prognosis of such patients

Methods: A case of anti-GABA_BR-associated encephalitis with refractory hyponatremia and small-cell lung cancer was reported. The clinical manifestations, assistant examinations diagnosis and treatment and prognosis were reviewed and analyzed. Combined with the review of relevant literature, the possible mechanism was explored.

Results:The patient was an elderly woman who went to the hospital because of "episodic unconsciousness with limb twitching",and soon progressed to status epilepticus accompanied by mental abnormalities and cognitive impairment, The anti-GABA_BR antibodies were detected in blood and cerebrospinal fluid. The refractory hyponatremia was observed. The cerebral MRl showed no obvious abnormality. The PET-CT image showed nodules and masses in the left hilar and lower lobe of the left lung with abnormal increase of ¹⁸F-fuorodeoxyglucose (¹⁸F-FDG metabolism). The small-cell lung cancer with mediastinal lymph node metastasis was diagnosed by percutaneous lung biopsy. After glucocorticoid impact therapy, intravenous infusion of gamma globulin, chemotherapy and radiotherapy for small-cell lung cancer, and symptomatic treatment for seizures, mental symptoms and hyponatremia, the seizures, mental symptoms and cognitive impairment were alleviated, but the hyponatremia still could not be corrected, and the lung cancer lesion gradually increased.In follow-up, it was found that the patient may have brain metastasis from small-cell lung cancer.

Conclusion: Anti-GABA_BR-associated encephalitis with refractory hyponatremia may be related to the abnormal secretion of antidiuretic hormone caused by autoimmunity or small-cell lung cancer, but its mechanism needs to be further explored.