Fig. 1.

Shoulder imaging of a 21 year-old man 24 hours following COVID vaccine injection. (A) Axial PDFS demonstrates edema in the deltoid muscle secondary to the primary injection site (Yellow Arrow); there is also inflammation with mild early adenopathy in the axillary region (Red Arrows). (B) Coronal T2 FS demonstrates edema in the deltoid muscle secondary to the primary injection site (Yellow Arrows); there is inflammation in the approximate location of the quadrilateral space (Red Arrows). (C) Coronal T2FS demonstrates prominence draining vessels and/or lymphatics extending from the deltoid inflammation (Yellow Arrows) to the region of the quadrilateral space (Red Arrow). (D) Coronal T1 images demonstrate an unusual increased T1 signal in the vessels and/or lymphatics extending to the approximate region of the quadrilateral space (Yellow Arrows). Color version of figure is available online.