Objective:

We describe a case demonstrating the importance of early dural biopsy in cases of hypertrophic pachymeningitis in a patient with aggressive disease course refractory to multiple immunosuppressive therapies.  

Background:

Hypertrophic pachymeningitis is a rare but increasingly encountered neurologic disorder characterized by either focal or diffuse pachymeningeal thickening.  The differential for this process is extensive but includes numerous treatable causes with emerging pharmacologic management options, including newly approved therapy for IgG4-related disease.  

Design/Methods:

N/A

Results:

A 17-year-old female presented after months of worsening headaches, right homonymous hemianopia, and seizure. Brain MRI revealed extensive pachymeningeal thickening suggestive of hypertrophic pachymeningitis. With unremarkable serologic, rheumatologic, and CSF evaluations, dural biopsy was performed with pathology revealing mixed chronic inflammatory infiltrates including lymphocytes and macrophages leading to subsequent diagnosis of idiopathic hypertrophic pachymeningitis (IHP). Repeat brain MRI revealed progressive hypertrophy, despite treatment with oral steroids.  Additional immunosuppressive treatment with pulse steroids, methotrexate, and azathioprine were administered, but her condition progressed, causing complete left eye vision loss before initiation of rituximab.  Given recent FDA approval for disease modifying therapy targeting IgG4 related disease and recalcitrant disease course, the patient underwent repeat dural biopsy to evaluate for candidacy of targeted immune modulating therapy. Unfortunately, there was no evidence of IgG4 related disease, solidifying the diagnosis of IHP.  

Conclusions:

Hypertrophic pachymeningitis is a rare neurologic disorder that can be secondary to numerous primary rheumatologic conditions. Among these, IgG4-related disease remains a challenging diagnosis, though one of vital importance given recent FDA approval of inebilizumab for treatment of such. This case demonstrates the value of early dural biopsy and exhaustive evaluation prior to determining idiopathic etiology in patients with hypertrophic pachymeningitis given the potential for aggressive phenotype of disease; reconsideration of diagnosis should be had for cases refractory to typical first line immunosuppression given recent therapeutic advances.