Inflammatory Pseudotumor of the Brain Parenchyma with IgG4 Hypergammaglobulinemia.

A 58-year-old woman with a 1-month history of right hand clumsiness and speaking difficulty was admitted to our hospital. A neurological examination revealed sensory aphasia and right hemiparesis. Her laboratory tests showed elevated serum levels of IgG and IgG4, pancytopenia, and liver dysfunction. The results of the imaging studies of her abdomen were compatible with sclerosing cholangitis. Brain MRI showed extensive signal abnormalities in the left hemisphere on T2-weighted and fluid-attenuated inversion recovery (FLAIR) images, extending from left internal capsule to the cerebral peduncle with an irregularly enhancing lesion in the left parietal lobe. A brain biopsy revealed lymphocyte and plasma cell infiltration and reactive gliosis. Most of the plasma cells were IgG positive; however, IgG4-positive plasma cells were sparsely observed. After the initiation of betamethasone treatment, her symptoms and the brain MRI abnormalities showed significant improvement. The brain biopsy results did not meet the current criteria of IgG4-related disease. This is the first reported case of a tumefactive lesion of the brain parenchyma with serum IgG4 elevation, which was responsive to steroid treatment. The accumulation of a greater number of reports on the pathological investigation of cases of possible IgG4-related disease may help to elucidate the exact role of IgG4 in IgG4-related disorders.