Fibromuscular dysplasia (FMD) is the abnormal development or growth of cells in the walls of arteries that can cause the vessels to narrow or bulge. The carotid arteries, which pass through the neck and supply blood to the brain, are commonly affected. Arteries within the brain and kidneys can also be affected. Narrowing and enlarging of arteries can block or reduce blood flow to the brain, causing a stroke. Some patients experience no symptoms of the disease while others may have high blood pressure, dizziness or vertigo, chronic headache, intracranial aneurysm, ringing in the ears, weakness or numbness in the face, neck pain, or changes in vision. FMD is most often seen in people age 25 to 50 years and affects women more often than men. More than one family member may be affected by the disease. The cause of FMD is unknown. Treatment is based on the arteries affected and the progression and severity of the disease. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.