Brainstem Encephalitis in Neuropsychiatric Systemic Lupus Erythematosus Mimicking Malignant Lymphoma: A Case Report and Literature Review.

We report a rare case of neuropsychiatric (NP) systemic lupus erythematosus (NPSLE) manifesting as brainstem encephalitis with generalized lymphadenopathy. A 32-year-old woman developed altered consciousness, fever, and pancytopenia, with diffusion-restricted brainstem lesions and elevated soluble interleukin-2 receptor (sIL-2R) levels in both serum and cerebrospinal fluid (CSF), accompanied by systemic lymphadenopathy and cytopenia, strongly mimicking malignant lymphoma. Histopathology excluded malignancy. The patient underwent immunosuppressive therapy with corticosteroids and cyclophosphamide, leading to marked neurological improvement. This case highlights the diagnostic challenge in differentiating NPSLE with brainstem involvement from lymphoproliferative disorders and underscores the importance of early biopsy and prompt immunosuppressive intervention to achieve favorable outcomes.