2026 American Academy of Neurology Abstract Website

Objective:

To present a case of hypertrophic pachymeningitis in a patient with elevated immunoglobulin G4 (IgG4) subclass and positivity for anti-myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA) initially misdiagnosed as central nervous system lymphoma (CNS) lymphoma.

Background:

IgG4-related disease is a systemic inflammatory condition marked by tumefactive lesions, often affecting the pancreas, orbits, and kidneys. Meningeal involvement is rare, seen in ~2% of cases. Similarly, MPO-ANCA-associated vasculitis typically involves kidneys and lungs, with few case reports of pachymeningeal disease. Both disorders can mimic malignancy due to non-specific constitutional symptoms and mass-like radiographic findings. This, combined with infrequent CNS presentation, often leads to delayed diagnosis and treatment.

Design/Methods:

Not applicable

Results:

A 44-year-old female with no past medical history presented with 8-months of progressive bilateral vision and hearing loss (complete loss on right side), new-onset diabetes mellitus, fevers, chills, and unintentional 20-pound weight loss. Magnetic resonance imaging of her brain revealed bifrontal dural thickening and asymmetric pachymeningeal enhancement. Cerebrospinal fluid results were unremarkable with exception of positive oligoclonal bands. Serum studies revealed elevated IgG4 (92 mg/dL) and positive MPO-ANCA antibodies. A lacrimal gland biopsy was inconclusive for definitive IgG4 or vasculitic pathology.

The patient received intravenous methylprednisolone for four days with improvement in ocular symptoms, then transitioned to rituximab for outpatient maintenance.

Conclusions:

Clinicians should be aware of neurologic manifestations of immune-mediated diseases - such as IgG4-related disease, MPO-ANCA-associated vasculitis, and their overlap syndromes - as they can closely mimic malignancy in both their clinical presentation and radiographic appearance, often leading to a delayed diagnosis and disease progression. We present a case of a woman with 8-months of progressive, inflammatory, and infiltrative process involving the pancreas, orbital adnexa, and pachymeninges, ultimately found to have elevated IgG4 and MPO-ANCA antibodies. Her condition responded well to immunosuppressive therapy, supporting an immune-mediated etiology.