IgG4-Related Disease: A New Etiology Underlying Diffuse Intracranial Dilating Vasculopathy

Diffuse intracranial aneurysmal vasculopathy is a rare condition, previously described in patients with human immunodeficiency virus infection. IgG4-related disease (IgG4-RD) is a recognized inflammatory disease of systemic organs, leading to fibrosis of connective tissues. It also has been linked to inflammatory dilating aortic aneurysms, coronary vascular disease, hypophysitis, orbital pseudotumor, and pachymeningitis. It has not yet been described as a cause of diffuse intracranial dilating vasculopathy. Histologically, this disease is characterized by IgG4-plasma cell infiltration, fibrosis, and phlebitis. A 40-year-old woman presented with acute heart failure, valvular insufficiency, and mycotic coronary aneurysms, concerning for endocarditis. Infectious workup was negative. Concurrent neurovascular workup revealed intracranial aneurysms, appearing mycotic in origin. Despite aggressive treatment for more than 5 years, she suffered multiple episodes of subarachnoid hemorrhage from a progressive dilating intracranial vasculopathy. Serum IgG levels and aneurysm wall pathology were consistent with IgG4-RD. This is the first reported case of a diffuse intracranial dilating vasculopathy secondary to IgG4-RD. Recognition of similar pathologic findings in clinical presentation and radiologic workup should prompt further rheumatologic workup and possible immunosuppressive therapies.