Diagnostic Dilemma of a Complex Case of Cerebral Vasculitis: A Rare Probable Drug-Induced Antineutrophil Cytoplasmic Antibody-Associated Vasculitis With Large Vessel Involvement.

A case of a 43-year-old male with a history of Graves' disease treated with propylthiouracil was investigated for vasculitis and lymphoproliferative disease. However, his clinical picture was complicated by recurrent episodes of neurological symptoms resembling stroke syndrome, which widened the breadth of the diagnostic workup. Extensive investigations, including imaging and biopsies, excluded other possibilities. The patient was treated as probable cerebral vasculitis after identifying new narrowing in the left middle cerebral artery and was treated with pulsed intravenous methylprednisolone, followed by high-dose oral prednisolone and cyclophosphamide. Repeated brain imaging showed further narrowing of the large vessels, which reaffirmed the likelihood of vasculitis necessitating continuation of induction therapy with further maintenance treatment, which led to stabilization of neurological burden and symptom recovery. This case elucidates complexities in reaching the diagnosis of drug-induced antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, which can present heterogeneously and mimic other clinical entities such as stroke.