During a stroke, there is an interruption in the blood supply followed by reperfusion which leads to histotoxic hypoxia because of an accumulation of reactive oxygen species (ROS).[4] In the case of inflammatory diseases, histotoxic hypoxia can also be triggered by ROS from mitochondrial damage in the active lesions of chronic multiple sclerosis. Inflammatory mediators such as heme oxygynase-1(HO-1) can result in histotoxic hypoxia when they are released in excess and cause the sequestration of iron as in the cases of Alzheimer's disease, Parkinson's disease and Multiple Sclerosis.[4]