A 73 year old caucasian woman with a past medical history of mammectomy for in situ breast cancer, appendectomy and spinal angioma, presented to her hematologist consultation in February 2022 with acute carotidynia, left otalgia, and fever. She had been diagnosed with intermediate-2 risk MDS and she had therefore started treatment with hypomethylating agents (chemical analog of cytidine - AZACYTIDINE) with complete remission obtained 6 months thereafter. Progression of MDS with 8% of blasts in the bone marrow in January 2022 led to the addition of inhibitor of BCL-2 protein (VENETOCLAX), in association with AZACYTIDINE that was still ongoing. She was diagnosed with SARS-COV2 infection on February 04, 2022, with cough and rhinitis without any fever. Since this was an immunocompromised patient, we treated this pauci-symptomatic SARS-COV2 infection (without the need for oxygen therapy) with an intravenous infusion of sotrovimab 500mg on February 05, 2022. She already received oral amoxicillin 1g twice per day prescribed by her general practitioner on February 04, 2022, and then the treatment was stopped the following day. On February 08, 2022, the patient displayed deep neutropenia (290/mm3) without fever and was treated with granulocyte colony-stimulating factor (NIVASTIM) for four days.

Before those events, last injection of AZACYTIDINE was performed on January 18, 2022 and last dose of VENETOCLAX was taken on January 26, 2022. COVID-19 PCR test remained positive

Odynophagia started February 10th, followed by left carotidynia on the 12th with swelling of the neck. Probabilistic antibiotherapy with macrolids was started on the 16^th in the hypothesis of an ear, throat and nose (ENT) infection, with no improvement. At her hematology consultation on February 18th: patient displayed fever at 38,5°C and elevation of the C-reactive protein at 328 mg/L(FIGURE A). A computed tomography (CT) scan performed the same day revealed tissue infiltration thickening surrounding the left internal carotid artery, the carotid bifurcation, the common carotid artery; as well circumferential thickening of the aortic arch (FIGURE B). Cervical ultrasound confirmed perivascular infiltration, maximum next to the internal carotid bifurcation/external as well as a harmonious left peri-carotid circumferential thickening. In the more anterior fat / region of cervical group II A, there was a well differentiated node, not suspicious. After disinfection, cytopunctures (2 passages) in the inter carotid region was performed. Cytology analysis found a largely hematic material consisting sheets of red blood cells associated with some figured elements of the blood, polynuclear and lymphocyte. No giant cell was visualized. No clearly identifiable tissue fragment was observed. No element of suspicious character was observed within the limits of these documents. The patient was transferred the same day to our internal medicine and vascular department.

Hypothesis of an infectious disease led to probabilistic broad-spectrum beta-lactam antibiotics. Examination revealed painful swelling of the neck with tenderness over his left carotid but had no vascular bruit. Other hypothesis was a large vessel vasculitis associated to MDS, Temporal arteries were normal, she had no headaches,arthralgias and blood pressure was symmetrical.

Oral cavity examination was normal. There were no thyroid nodules. Pulmonary and heart auscultation were normal. There were no skin rashes,

Ultrasound of the left internal carotid artery found isoechoic, circumferential wall thickening extending to the origins of the internal and external carotid arteries (figure C). There were no inflammatory halos of the temporal arteries. 18-FDG-TEP scanner showed hypermetabolism of the left carotid, circumferential hypermetabolism of the aortic arch, moderate hypermetabolism of the anterior wall of the aorta of its transdiaphragmatic passage.

Blood cultures and mycobacterial blood cultures were sterile. EBV specific serology showed past infection. HIV, HVC, HVB and syphilis serologies were negative. Increased alpha-1 and alpha-2 were detected on protein electrophoresis. Determination of immunoglobulins and subclasses were normal. Serum complement C3 and C4 normal.

Inflammatory syndrome decreased as well as neck tenderness. It was decided to not introduce steroids due to spontaneous evolution. Broad spectrum antibiotics were stopped after five days. Ultrasound control 7 days later showed diminished thickening infiltration. 1 month and half later (45 days later) in April 2022 : CT scanner (FIGURE D) and ultrasound showed clear regression of the periaortic infiltration at the level of the aortic arch and the isthmus but persistent periaortic thickening of the descending aorta. C reactive protein returned to normal.

Hematologists collegially decided a therapeutic pause due to recent events with no reintroduction of azacytidine nor venetoclax and filgrastim. After 6 months of follow-up, she remains free from disease progression with persistent asymptomatic moderate bicytopenia (neutrophils 1200/mm3, platelets 40 000/mm3).