Overlapping syndrome with concomitant mGluR2-Ab and GFAP-Ab: A case report

An 11-year-old male patient presented with acute neurological deterioration, including meningitis, encephalitis, and myelitis. Initial testing detected antibody against metabotropic glutamate receptor 2 (mGluR2-Ab); retesting identified coexisting anti-glial fibrillary acidic protein antibody (GFAP-Ab). Pathogenic examinations were negative. The patient received a combination of immunotherapies, including intravenous methylprednisolone pulse therapy, human immunoglobulin pulse therapy, and plasma exchange. Five months after onset, the patient showed a favorable prognosis, though a residual neurogenic bladder remained. We present the first documented case of overlapping autoimmune syndrome with concurrent mGluR2-Ab and GFAP-Ab. The coexistence of these antibodies can lead to a wide range of clinical manifestations, including simultaneous GFAP-Ab-related meningoencephalomyelitis and mGluR2-Ab-related ataxia. This complexity complicates diagnosis and treatment, underscoring the need for a comprehensive understanding of the pathogenic mechanisms of these antibodies and timely combined immunotherapy. Additionally, this case suggests that mGluR2-Ab and GFAP-Ab may serve as the jointly responsible antibodies for this condition.