Cerebral cavernous malformation (CCM) is a cluster of malformed and tangled blood vessels in the brain, which was previously assumed to be genetic. Patients with CCM can be asymptomatic; or can have long-term health problems, including headaches, epilepsy, stroke, and death. In 2017, a multistate study, in mice, found gram-negative bacteria activated TLR-4; which was the molecular mechanism in endothelial cells that underlies formation of CCM.

CCM and Alzheimer’s have similar findings, in the brain—abnormal and tangled blood vessels, neuronal degeneration, glial cell proliferation, neurofibrillary tangles, and sclerosis in hippocampal cells. Chlamydia pneumonia is a gram-negative bacteria, which can attack endothelial tissue, blood vessels, and the brain; and has repeatedly been identified in studies of Alzheimer’s brains. Some forms of chlamydia also induce excess TLR-4.  Chlamydia infection is a likely cause of CCM.