Primary large B-cell lymphoma of the central nervous system with positive NMDAR antibody: a case report

N-methyl-D-aspartate receptor (NMDAR) is an ionotropic glutamate (Glu) receptor that is widely expressed in the central nervous system (CNS), mainly in the hippocampus. We present a case in which the patient had atypical clinical manifestations and was positive for anti-NMDAR antibodies.

A 40-year-old male was admitted to the hospital with "dizziness and double vision for 2 months". At admission, the patient was lethargic, had short-term memory loss, exhibited loss of orientation (time, place, and person) and calculation ability, and had limited left eye abduction. After admission, serum anti- NMDAR antibody was 1:32, and cerebrospinal fluid was 1:1. Magnetic resonance imaging (MRI) revealed diffuse abnormal signals in the bilateral basal ganglia, thalamus, brainstem, hippocampus, and temporal lobe, with patchy and heterogeneous enhancement. A stereotactic brain biopsy was performed, and the pathological results indicated normal brain tissue. Preliminary diagnosis suggested anti-NMDAR antibody encephalitis. The patient was treated with methylprednisolone combined with intravenous gamma globulin; the symptoms were alleviated, and the patient was discharged. Two months later, the patient's symptoms worsened, and a second stereotactic brain biopsy was performed. The pathological results showed that the patient had primary diffuse large B-cell lymphoma of the CNS, and the patient was transferred to the Department of Hematology and received chemotherapy combined with rituximab. The patient was in stable condition.

When the primary CNS diffuses large B-cell lymphoma is associated with autoimmune encephalitis, it is very easy to be misdiagnosed. The diagnosis should not be based on the pathological examination that was performed in the early stage of the disease. Therefore, in the diagnosis of immune diseases caused by nervous system infections, it is necessary to dynamically observe the evolution of the disease, perform differential diagnoses when necessary, and ultimately improve our understanding of the disease.