A Case of Microscopic Polyangiitis Presenting as Cranial Giant Cell Arteritis

We present a case of a 63-year old man with microscopic polyangiitis (MPA) in which the initial clinical presentation resembled the cranial form of giant cell arteritis (GCA) (headache, jaw claudication, low grade fever and raised inflammation markers). Ultrasound of both superficial common temporal arteries revealed signs indicative of vessel wall inflammation. Based on clinical picture and compatible imaging findings, treatment with corticosteroids for GCA was started. After initial improvement and steroid tapering, lung infiltrations, mononeuritis of the right peroneal nerve and cutaneous necrosis appeared and p-Antineutrophil cytoplasmic antibodies (ANCA) turned out to be positive. Three intravenous cyclophosphamide pulses for MPA led in disease remission and maintenance treatment with azathioprine followed. Two years later, the patient has no symptoms and laboratory parameters are normal. This case highlights that MPA can affect temporal arteries and can masquerade as cranial GCA.