190. You can only treat what you see: the key role of imaging in vasculitis

Presentation of Case: The case of a 69-year-old gentleman is presented, with known cardiovascular risk factors, and a previous ischemic heart disease with preserved ejection fraction. In addition, the patient had been diagnosed with rheumatic polymyalgia a year before, having been treated with a low dose of corticosteroids since then. The patient was admitted to the Emergency Room with a two month fever and headache history, complaining of malaise and arthromyalgias. The patient also presented a black spot in the left arm accompanied by a pruriginous rash in the left trunk without referring any insect bites. Although Borrelia burgdorferi´s serology was negative, the patient was empirically treated with doxycycline, with a good response of arthromyalgias, although with persistent fever. Moreover, the patient acknowledged significant weight loss, being admitted to the Internal Medicine ward for further testing.

Diagnostic Testing: Initial patient evaluation focused on ruling out an infectious disease as the cause of the patients’ symptoms. Therefore, numerous viral and bacterial serologies with a COVID-19 PCR test and lumbar puncture were performed, with negative results. Blood cultures were as well negative. Laboratory results showed an elevation of inflammatory markers such as an Erythrocyte Sedimentation Rate (ESR) level of 120 mm/hour, and a C - Reactive Protein (CRP) level of 200 mg/L, accompanied by normocytic normochromic anemia with hemoglobin of 11 g/dL and ferritin of 1500 µg/L. Further study of the patient was reached with a cranial, chest and abdominal computerized tomography (CT) scan, with no findings. Due to the persistence of inflammatory markers and fever, a PET scan was requested with a result of a hypermetabolic caption in large vessels (aortic, both carotids, subclavian and, to a lesser extent, in the iliac axes) being compatible with the diagnosis of giant cells arteritis (GCA) (Figure 1).

Differential & Final Diagnosis: Fever, presence of inflammatory markers and the imaging results were the clue of the differential diagnosis, suggesting a large vessel vasculitis. The two principal causes of this type of vasculitis are Takayasu's arteritis (TAK) and giant cells arteritis (GCA). The former was ruled out due to the epidemiology, headache and rheumatic polymyalgia prior history. The differential diagnosis of patients with inflammatory vascular diseases is crucial. It should include infectious diseases such as aortitis (like mycobacterial or syphilis aneurisms). Furthermore, other autoimmune disorders must be ruled out, for example Behçet’s disease, and atherosclerosis, IgG4-related disease also considered. In this clinical case, four out of five diagnostic criteria for GCA were accomplished. These criteria were the age older than 50, the recent history of headache, Erythrocyte Sedimentation Rate elevation over 50 mm/hour and aortic involvement in PET scan.

Discussion of Management: The challenge of this clinical case is the differential diagnosis between the two principal large vessel arteritis, which are Takayasu's arteritis and giant cell arteritis. Treatment consists in high-dose corticoid therapy associated with tocilizumab or methotrexate. In the case presented, treatment with 60 mg of prednisone once daily was started, with the administration of calcium and vitamin D to prevent osteoporosis. As a glucocorticoid sparing agent, methotrexate 2.5 mg once weekly was also initiated, with folic acid supplements. In further follow up the patient kept asymptomatic with normalization of acute phase reactants. Glucocorticoid tapering dosage until maintenance treatment with prednisone 2.5 mg once daily was achieved, also with a decreasing methotrexate dosage.

Conclusion: Vasculitis diagnosis is a challenging process due to the lack of pathognomonic signs and frequent overlap between different diseases. Furthermore, GCA diagnosis is also hardened due to its late clinical presentation. Diagnosis must focus on the established classification criteria, supported by epidemiology and biopsy results in order to guide clinical practice. However, the fulfillment of all diagnostic criteria is not common. Therefore, more objective tests such as biopsy results and specific imaging tests, and clinical response to inmunosupresive treatment are crucial to diagnostic confirmation.

Disclosures: None.

Figure 1. PET scan results