Delayed Diagnosis of Recurrent IgG4-Related Hypertrophic Pachymeningitis: From an Isolated Thoracic Lesion to Multilevel Craniospinal Involvement

Immunoglobulin G4 (IgG4)-related hypertrophic pachymeningitis (IgG4-RHP) is a rare manifestation of IgG4-related disease (IgG4-RD) that can mimic other space-occupying lesions and may go unrecognized without a high index of suspicion.We describe a 74-year-old woman who presented with progressive bilateral lower-extremity weakness caused by a dorsal epidural mass at T1-6.An epidural hematoma was initially suspected, and emergency laminectomy was performed.Histopathological examination revealed nonspecific fibrous tissue.IgG4-RD was not considered, and IgG4 immunohistochemical staining (IHC) was not performed.Approximately 20 months later, lesions recurred at T8 and T12, with extensive dural hypertrophy extending from the skull base to C2 and surrounding the cerebellum.The patient underwent further surgical decompression at T8. IHC of both the recurrent and archived specimens revealed dense infiltration of IgG4-positive plasma cells; an elevated serum IgG4 level further supported the diagnosis.After surgery and corticosteroid therapy, magnetic resonance imaging at 2 months showed marked regression of the dural lesions.No clinical or serological evidence suggestive of recurrence was documented during approximately 3 years of follow-up.This case illustrates the difficulty of diagnosing IgG4-RHP and the importance of considering it in patients with recurrent or unexplained dural lesions, particularly when initial histopathological findings are nonspecific.