Coexistence of IgG4-Related Hypertrophic Pachymeningitis and Anti-NMDA Receptor Encephalitis: A Rare Clinical Presentation

Abstract We present a case study involving a 53-year-old male patient exhibiting a unique combination of IgG4-related hypertrophic pachymeningitis (IgG4-RHP) and anti-NMDA receptor encephalitis. The patient's clinical manifestations, characteristics, and laboratory findings collectively showcased features characteristic of both IgG4-RHP and anti-NMDA receptor encephalitis. The patient's clinical course was marked by a diverse array of symptoms, encompassing progressive visual impairment, recurrent psychiatric and behavioral disruptions, left upper limb weakness, and radiological indications of diffuse dural thickening with prominent enhancement, coupled with diffuse cerebral edema. During the acute phase, the patient presented with a mildly elevated serum IgG4 level, and cerebrospinal fluid (CSF) analysis yielded positive results for NMDA antibodies. Histopathological assessment of the pachymeninges revealed fibroblastic proliferation accompanied by localized lymphocytic infiltration. Treatment involving corticosteroid administration led to significant alleviation of the patient's clinical symptoms and MRI-detected abnormalities. To our best knowledge, there are no analogous instances documented in existing literature. Further clinical investigations and neuropathological studies are imperative to elucidate the underlying mechanisms and determine optimal therapeutic strategies for managing this distinctive coexisting condition.