Central Nervous System Peripheral T Cell Lymphoma Manifesting as Lymphomatosis Cerebri That Was Misdiagnosed as Neuro-Behçet's Disease: A Case Report

BACKGROUND: Lymphomatosis cerebri (LC) is a unique form of primary central nerves lymphoma (PCNSL), which presents as diffuse infiltration of lymphoma cells characteristically in the white matter rather than tumor formation. However, the involvement of central nervous system (CNS) is unclear because of the lack of contrast enhancement. CASE PRESENTATION: We treated a 53-year-old woman with LC and brain lesions resembling neuro-Behcet's disease. She had a past history of acute uveitis and current symptoms of somnolence and gait disturbances progressing for one month. Cranial magnetic resonance imaging (MRI) revealed high signal lesions in the brain stem. Based on her past history and present clinical findings, she was clinically diagnosed with neuro-Behcet's disease, which was treated with 1 g of methylprednisolone (mPSL) pulse therapy. Repeated mPSL pulse therapy resulted in a minor response, but the cerebral lesions persisted. After a short remission of several months, signal changes of the brain stem lesion recurred and her consciousness level worsened at 4 months after diagnosis. Upon admission to our hospital, positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose integrated with computed tomography revealed abnormal uptake in the systemic lymph nodes (LNs), including the bilateral inguinal LNs. A diagnosis based on a biopsy of the left inguinal LNs was primary central nervous system lymphoma with inguinal LN lesions, manifesting as LC from malignant peripheral T cell lymphoma, not otherwise specified. Four courses of high-dose methotrexate (3.5 g/m(2)) therapy lead to temporary recovery of consciousness, but there was no improvement in other neurological findings. All nodal lesions tentatively regressed. Serum soluble interleukin-2 receptor (sIL-2R) (normal range: 121–613 U/mL) was constitutively decreased from 8,520 U/mL before chemotherapy to 740 U/mL after chemotherapy. We observed cerebral micro-bleeds in the center of LC lesions during chemotherapy, but no surgical intervention was required. Two months later, LC recurred in the brain, which was fatal. CONCLUSIONS: Neuro-Behçet's disease is difficult to distinguish from LC when other clinical findings, including human leukocyte antigen disparity, serum sIL-2R, or cerebrospinal IL-6, are lacking. LC should be differentiated from CNS lymphoma before corticosteroid therapy.