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  • Melena: Black stool due to bleeding in the stomach or the duodenum. Dark stool may also be caused by oral iron therapy.
  • Migraine: A type of headache often characterized by a preliminary change in vision (aura) followed by severe headaches. They are particularly common in patients with HHT and lung AVM(s).
  • Morbidity: To have significant symptoms or complications from a disease or a treatment.
  • MRA: (Magnetic Resonance Angiography) An MRI technique designed to view the major arteries of the brain.
  • MRI: (Magnetic Resonance Imaging) A scan of the brain (or other organ) which does not use radiation, but uses magnetic energy to determine the presence of AVMs, aneurysms, stroke and brain abscess.
  • Mucous Membrane: Also called the mucosa. The lining of the body cavities that connects with the outside air. For example, the lining of the nose or mouth.
  • Mutation: A change in the code of a gene, which can cause a genetic disorder.