IgG4-related pachymeningitis mimicking meningiomas

A 54-year-old male patient had a sudden convulsion of the left limb which rapidly progressed from the fingertip to the left limb, followed by loss of consciousness. He did not experience any signs or symptoms such as headache, speech disturbance, chest pain, palpitation, or other discomforts before the attack. Neurological examination after the patient was admitted to the hospital was negative. The initial computed tomography (CT) of the brain showed an uneven mass beneath the medial plate of the skull in the right frontal junction area with a size of about 2.6 cm × 2.2 cm, the CT value was about 55Hu (Fig. 1). The magnetic resonance imaging (MRI) demonstrated a subdural lesion that was isointense to grey matter on T1WI and low intense on T2WI, with surrounding vasogenic edema. Post-gadolinium contrast-enhancement of the lesion demonstrated dramatic homogeneous enhancement with an apparent “dural tail” (Fig. 2A–C, arrowheads). The intraoperative appearance of the mass showed severe erosion of the surrounding dura and skull, the anterior central gyrus was most affected. Postoperative histopathology revealed a dense plasma cell infiltration and a few lymphocytes and neutrophils in the dura (Fig. 3A), immunohistochemistry showed an increased number of IgG4 cells (> 50 /HPF) (Fig. 3B arrowheads). The patient's serum IgG4 level was 37.1 mg/dL after resection one month later (reference value 3.9–86.4 mg/dL). Investigation for other systemic manifestations of IgG4-related disease was negative. After 6 months of follow-up, IgG4-related hypertrophic pachymeningitis was diagnosed.