Immunoglobulin G4-related disease in an elderly patient with treatment-resistant headache: a case report.

Immunoglobulin G4 (IgG4)-related disease is an immune-mediated, fibroinflammatory condition that causes multisystemic contrast enhancement and is predominantly observed in elderly male patients. The most prominent features of IgG4-related disease are systemic involvement affecting from two to six systems. In the central nervous system, these contrast enhancements are typically found in the meninges and orbit. This case study describes a 78-year-old female patient with persistent headaches and constant diarrhea who underwent treatment for IgG4-related disease. Despite two months of treatment with non-steroidal and opioid analgesics, the patient remained unresponsive and continued to experience diarrhea for 4 months. Brain magnetic resonance imaging revealed contrast enhancement in the leptomeningeal surfaces, and a biopsy of the gastrointestinal mucosa confirmed the diagnosis of IgG4-related disease, showing widespread plasma cell infiltration and IgG4 expression on plasma cells. The patient was initially treated with 1.0 g/day of pulse therapy for 5 days, followed by a maintenance dose of 1.0 mg/kg oral azathioprine. When azathioprine caused significant pancytopenia, rituximab therapy was initiated. The patient's headaches resolved completely, and the diarrheal attacks were controlled. This case highlights the importance of considering IgG4-related disease as a potential cause of headache or multiorgan symptoms in elderly patients with new-onset headache unresponsive to conventional analgesics. IgG4-related disease can often be effectively treated with steroids and monoclonal antibodies.