A 35-year-old woman presented with acute signs of stroke (appendix e-1 on the Neurology® Web site at www.neurology.org). After initial CT with angiography, MRI with time-of-flight angiography confirmed agenesis of both internal carotid arteries (ICA; figure 1A). It revealed bilateral vertebral artery (VA) dissections and ischemias in both middle artery territories (figure 1, A-E). Skin biopsy microscopy (figure 2) was consistent with ultrastructural connective tissue syndrome (uCTD), for which no further evidence was found apart from mild hypermobility of the finger joints. The underlying uCTD with structural instability of the arterial walls and, due to the bilateral ICA agenesis, the increased blood flow in the vertebrobasilar circulation may have promoted VA dissection.