Central nervous system involvement by non-nodal mantle cell lymphoma masquerading as autoimmune encephalitis versus paraneoplastic syndrome

To the Editor:Mantle cell lymphoma (MCL) is a relatively rare neoplasm of mature B-cells.Its hallmark genetic feature is Cyclin D gene rearrangement, most commonly t(11; 14)(q13; q32) leading to CCND1::IGH translocation. 1 MCL is generally an aggressive disease, with most patients presenting with an advanced clinical stage (III or IV) and B symptoms. 2 While lymph nodes are typically the primary site of disease, MCL often involves extranodal sites, including the spleen, bone marrow, peripheral blood, and gastrointestinal tract. 2 Central nervous system (CNS) involvement is rare, documented in less than 1% of cases at the time of presentation, and 2%-4% of cases overall. 3,4 Here, we report a unique case of MCL in a 67-yearold woman who presented with neurologic symptoms mimicking autoimmune encephalitis and paraneoplastic syndrome.The patient had a progressive course and passed away, with MCL ultimately diagnosed at autopsy.The absence of clinical nodal involvement and negative SOX11/CD5 immunoreactivity were suggestive of the non-nodal MCL subtype. 1,5 To our knowledge, this is the first report documenting CNS involvement in this typically indolent subtype of MCL.A 67-year-old woman developed insidious, progressive neurologic symptoms over several months, including fatigue, brain fog, foot numbness, unsteadiness, and intermittent diplopia.An ophthalmologic evaluation was unremarkable.Her symptoms acutely worsened several months later, necessitating hospitalization.She had developed new-onset confusion, memory loss, dysphagia, and an abnormal gait.Additionally, she experienced episodes of hypoglycemia, hypothermia, and unresponsive, incoherent spells lasting up to 15 minutes.