Autoimmune GAD-positive rhombencephalitis with rare manifestation: a case report and literature review

GAD-positive rhombencephalitis is a rare autoimmune neurological disorder characterized by the presence of antibodies targeting glutamic acid decarboxylase (GAD), an enzyme essential for neurotransmitter regulation. This case report presents a 43-year-old male patient with progressive neurological symptoms, including gait instability, cranial nerve palsy, dysphagia, dysarthria, and hydrophobia. Diagnostic evaluation showed a modest elevation in serum anti-GAD antibodies, while brain MRI demonstrated mild cerebellar atrophy. Electroencephalography (EEG) revealed multifocal slowing and sharp wave activity in the bitemporal and central regions, consistent with diffuse cerebral dysfunction without epileptiform discharges. In addition, an extensive workup was performed to exclude infectious, metabolic, paraneoplastic, and alternative autoimmune etiologies. Initial treatment with pulse corticosteroids and intravenous immunoglobulin (IVIG) provided partial symptom relief; however, the patient subsequently experienced respiratory distress and pneumonia, requiring intensive care intervention. The clinical presentation in this case exemplifies the diagnostic intricacy of anti-GAD antibody-related disorders, which frequently exhibit symptoms that overlap with other autoimmune and infectious encephalitis. This case illustrates the value of identifying unique manifestations such as hydrophobia, which has not been previously reported in the context of anti-GAD rhombencephalitis. Treatment focused on immunotherapy, including high-dose corticosteroids and plasmapheresis, while emphasis was placed on vigilant management of potential complications and concurrent autoimmune conditions. This report contributes to the understanding of anti-GAD antibody-related neurological syndromes and highlights the importance of a multidisciplinary approach in managing these complex cases.