igg4-related disease is a recently defined disorder characterized by an inflammatory reaction rich in igg4-positive plasma cells associated with sclerosis4 ) .
this disease includes autoimmune pancreatitis , mikulicz disease , pseudotumor of the lung , tubulointestinal nephritis , and riedel thyroiditis4 ) .
central nervous system involvement is extremely rare , and the most commonly reported location is the pituitary gland4 ) .
hypertrophic pachymeningitis is an uncommon disorder that causes a localized or diffuse thickening of the dura mater10 ) .
rare cases of dural spinal involvement by igg4-related screlosing disease have also been reported1,2 ) , and recently , the possibility that igg4-related sclerosing disease may underlie some cases of intracranial hypertrophic pachymeningitis has also been suggested .
however , only 9 cases of intracranial hypertrophic pachymeningitis related to igg4 infiltration have been reported in the literature3,5,6,7,8,9,11 ) .
we herein report an additional case of igg4-related intracranial hypertrophic pachymeningitis proved by both local infiltration of plasma cells and igg4/igg ratio in surgical specimen .
a 45-year - old , previously healthy male presented with focal seizure of left extremities with generalization . on admission , his neurological examination was normal .
mri revealed irregular dural thickening and a marked enhancement of the right parieto - occipital dura and falx ( fig .
1 ) . whole - body 2-[f]-fluoro-2-deoxy - d - glucose positron emission tomography scanning demonstrated no abnormal hyperuptake , in the whole body , including the brain and dura .
the preoperative differential diagnoses included meningioma en plaque , lymphoma , tuberculosis , sarcoidosis , collagen vascular disorders , lymphoma , meningeal carcinomatosis diseases and igg4-related disease .
the mass in the convexity dural region was resected , while the mass adjacent to the superior sagittal sinus and falx was not removed . in the surgically resected specimens , a solid yellow to white - colored lesion measuring 35336
histologically , the solid lesion consisted of a proliferation of fibroblast - like spindle cells and an infiltration of mononuclear cells , including predominantly plasma cells , with abundant collagenous tissue ( fig .
for immunohistochemistry , we used monoclonal antibodies against igg and igg4 . in the immunohistochemical study ,
most of the plasma cells infiltrating into the sclerosing lesion were found to be igg - positive [ igg4-positive plasma cells / high power field ( hpf ) , 78 ] , and the ratio of igg4-positive plasma cells to the overall igg - positive cells was 45% in the area containing the highest infiltration of plasma cells ( fig .
on the basis of the above findings , igg4-related sclerosing disease arising from the dura mater was suspected .
thus , we evaluated a patients ' serum igg4 level and it was 51 mg / dl ( normal range , 4.8 - 105.0 mg / dl ) .
the patient 's postoperative course was uneventful , and no radiological or clinical signs of recurrence were noted 12 months after performing a surgical resection ( fig .
only 10 cases have been reported in the literature , including the present case3,5,6,7,8,9,11 ) .
the ages of the patients ranged from 26 to 75 years ( mean , 51.9 years ) .
the serum igg4 levels were evaluated in four patients , and elevated igg4 level was observed in one patient .
steroid treatment was started prior to surgery in one case , and after surgery in seven cases .
however , some researchers have recommended a cut - off level for the absolute number of igg4-positive cells at > 50/hpf , and the ratio of igg4-positive cells / igg - positive cells > 40%4 ) .
the elevation of the serum igg4 levels is not mandatory for the diagnosis , because the serum igg4 level often correlates with the disease activity and the number of involved organs , but the levels may also be normal4 ) .
our patient met the above diagnostic criteria . additionally , our literature review suggested that serum igg4 level may be normal in most patients with igg4-related intracranial hypertrophic pachymeningitis .
however , conservative observation can also be applied in some patients . as a result , we therefore put adjuvant steroid therapy on hold for our patient .
some authors have suggested that a biopsy , followed by steroid treatment , may be safe and valid7,8 ) .
however , due to their rarity , there is no unified treatment protocol for such cases . to date , it remains unclear whether biopsy or partial / subtotal resection is better , and whether steroid treatment is necessary . in our patient , easily resectable lesion was removed , whereas we consider that biopsy might be sufficient to obtain definitive diagnosis .
we suggest that igg4-related disease should be added to the pachymeningitis spectrum , even when serum igg4 level is normal .
 hypertrophic pachymeningitis is an uncommon disorder that causes a localized or diffuse thickening of the dura mater . 
 recently , the possibility that igg4-related sclerosing disease may underlie some cases of intracranial hypertrophic pachymeningitis has been suggested . 
 we herein report the tenth case of igg4-related intracranial hypertrophic pachymeningitis and review the previous literature . a 45-year - old male presented with left - sided focal seizures with generalization . magnetic resonance imaging ( mri ) revealed a diffuse thickening and enhancement of the right convexity dura matter and falx with focal nodularity . 
 the surgically resected specimens exhibited the proliferation of fibroblast - like spindle cells and an infiltration of mononuclear cells , including predominantly plasma cells . 
 the ratio of igg4-positive plasma cells to the overall igg - positive cells was 45% in the area containing the highest infiltration of plasma cells . on the basis of the above findings , 
 igg4-related sclerosing disease arising from the dura mater was suspected . 
 igg4-related sclerosing disease should be added to the pachymeningitis spectrum . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION