Case Report: Overlapping multiple sclerosis and neuropsychiatric systemic lupus erythematosus with positive MOG-IgG: a case initially misdiagnosed as depression.

We present a 69-year-old female patient who initially manifested with depression and anhedonia, initially misdiagnosed as primary psychiatric illness. She subsequently developed progressive gait instability and cognitive decline. After comprehensive clinical and laboratory evaluation, she was finally diagnosed with multiple sclerosis (MS) complicated by neuropsychiatric systemic lupus erythematosus (NPSLE). Brain magnetic resonance imaging (MRI) revealed multifocal white matter lesions consistent with demyelination. Serologic testing demonstrated positivity for antinuclear antibody (ANA), anti-double-stranded DNA (dsDNA), anti-SS-A/Ro, anti-histone, anti-nucleosome, and anti-centromere antibodies. Cerebrospinal fluid (CSF) examination confirmed intrathecal synthesis of immunoglobulin G (IgG), as evidenced by CSF-restricted oligoclonal bands (OCBs). Serum myelin oligodendrocyte glycoprotein immunoglobulin G (MOG-IgG) was positive at a titer of 1:32, whereas aquaporin-4 (AQP4) antibodies were negative. Based on the clinical manifestations, laboratory results and disease progression, the final diagnosis was established as coexisting MS and NPSLE. The patient achieved clinical improvement after treatment with glucocorticoids and hydroxychloroquine. This case highlights the diagnostic challenges posed by overlapping autoimmune central nervous system (CNS) disorders and underscores the importance of longitudinal assessment in differentiating MS from MOG-IgG-associated disorder (MOGAD) and NPSLE.