摘要：

Lymphomatoid granulomatosis (LYG) is a rare, T-cell-rich Epstein–Barr virus (EBV)-positive B-cell lymphoproliferative systemic disease. Only a few cases of LYG have been described in patients with autoimmune disorders, with only one case described in a patient with systemic lupus erythematosus (SLE). However, no cases of isolated central nervous system (CNS)–LYG have been reported in patients with autoimmune diseases. Since isolated CNS involvement is rare, its clinicopathological features remain incompletely understood. Herein, we report about an 85-year-old Japanese woman who was diagnosed with SLE 26 years ago and was stable and maintained on prednisone (5 mg/day) for 20 years. Twenty-six days before admission, she developed cognitive dysfunction. Brain magnetic resonance imaging (MRI) revealed multiple nodular lesions with ring-like enhancements seen on gadolinium-enhanced T1-weighted imaging. A brain biopsy was performed on the right frontal lobe lesion. Pathological findings revealed T-cell infiltration surrounding the blood vessels with fibrin deposition, a few multinucleated cells, and large atypical cells with prominent nucleoli. Large atypical cells positive for CD20 and EBV-encoded RNA were seen at a density of >100 cells per high-power field. Based on laboratory testing, imaging, and pathology findings, the patient was diagnosed with Grade III LYG. Treatment with tirabrutinib (480 mg once daily) was started. The patient achieved clinical response to treatment, as evidenced by improved mental status. In patients with SLE who present with multiple nodular or ring-like lesions on brain MRI, a brain biopsy with histological diagnosis is crucial for the exclusion of CNS–LYG.

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