Multifocal Inflammatory Pseudotumor Involving the Orbit, Skull Base, and Cauda Equina Causing Progressive Visual Loss...

Inflammatory pseudotumor (IPT) is a rare benign inflammatory mass lesion characterized by inflammatory cell infiltration and fibroblastic proliferation. Although IPT can occur in various organs, central nervous system (CNS) involvement is rare. We report a case of multifocal IPT involving the orbit, skull base, and cauda equina in a patient with a well-controlled HIV infection. A man in his 50s with a 13-year history of HIV infection presented with progressive visual impairment. His HIV viral load remained undetectable under antiretroviral therapy, with CD4-positive lymphocyte counts consistently above 400/μL. Serial magnetic resonance imaging demonstrated enlargement of the skull base and orbital lesions over two months, together with the appearance of additional lesions involving the optic chiasm, pituitary region, cervical spinal canal, and cauda equina. Cerebrospinal fluid examination revealed lymphocytic pleocytosis, without evidence of malignancy or infection. Biopsies of the lacrimal gland and cauda equina revealed inflammatory lymphocytic infiltration without evidence of lymphoma, IgG4-related disease, or other neoplastic disorders. Based on the clinicopathological and radiological findings, a diagnosis of multifocal IPT was established. No corticosteroid or disease-specific therapy was administered before histopathological confirmation because the diagnosis remained uncertain. Following the diagnosis of multifocal IPT, the lesions stabilized without specific treatment despite severe visual loss. This case highlights IPT as a rare differential diagnosis of multifocal CNS lesions in patients with HIV infection, even in the setting of sustained virological suppression and immune reconstitution. Rapid disease progression was temporally associated with recent COVID-19 infection; however, a causal relationship could not be established.