MRI studies in HD patients showed an increase BBB permeability to Gd-DTPA (~550 Da), and postmortem analysis showed an increase in fibrin deposition in the brain parenchyma associated with a significant reduction in occludin and claudin-5 expression at the BBB (Drouin-Ouellet et al., 2015). The gene discussed is CLDN5; the disease is Huntington disease.