Moyamoya disease

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What is moyamoya disease?

Moyamoya disease is a disorder of blood vessels in the brain, specifically the internal carotid arteries and the arteries that branch from them. These vessels, which provide oxygen-rich blood to the brain, narrow over time. Narrowing of these vessels reduces blood flow in the brain. In an attempt to compensate, new networks of small, fragile blood vessels form. These networks, visualized by a particular test called an angiogram, resemble puffs of smoke, which is how the condition got its name: "moyamoya" is an expression meaning "something hazy like a puff of smoke" in Japanese.

Moyamoya disease commonly begins either around age 5 or in a person's thirties or forties. A lack of blood supply to the brain leads to several symptoms of the disorder, including temporary stroke-like episodes (transient ischemic attacks), strokes, and seizures. In addition, the fragile blood vessels that grow can develop bulges (aneurysms), or they can break open, leading to bleeding (hemorrhage) in the brain. Affected individuals may develop recurrent headaches, involuntary jerking movements (chorea), or a decline in thinking ability. The symptoms of moyamoya disease often worsen over time if the condition is not treated.

Some people have the blood vessel changes characteristic of moyamoya disease in addition to features of another disorder, such as neurofibromatosis type 1, sickle cell disease, or Graves disease. These individuals are said to have moyamoya syndrome.

How common is moyamoya disease?

Moyamoya disease was first identified in Japan, where it is most prevalent, affecting about 5 in 100,000 individuals. The condition is also relatively common in other Asian populations. It is ten times less common in Europe. In the United States, Asian Americans are four times more commonly affected than whites. For unknown reasons, moyamoya disease occurs twice as often in females as in males.

What genes are related to moyamoya disease?

The genetics of moyamoya disease are not well understood. Research suggests that the condition can be passed through families, and changes in one gene, RNF213, have been associated with the condition. Other genes that have not been identified may be involved in moyamoya disease. It is also likely that other factors (such as infection or inflammation) in combination with genetic factors play a role in the condition's development.

The RNF213 gene provides instructions for making a protein whose function is unknown. However, research suggests that the RNF213 protein is involved in the proper development of blood vessels.

Changes in the RNF213 gene involved in moyamoya disease replace single protein building blocks (amino acids) in the RNF213 protein. The effect of these changes on the function of the RNF213 protein is unknown, and researchers are unsure how the changes contribute to the narrowing of blood vessels or the characteristic blood vessel growth of moyamoya disease. For unknown reasons, people with moyamoya disease have elevated levels of proteins involved in cell and tissue growth, including the growth of blood vessels (angiogenesis). An excess of these proteins could account for the growth of new blood vessels characteristic of moyamoya disease. It is not clear if changes in the RNF213gene are involved in the overproduction of these proteins.

How do people inherit moyamoya disease?

Up to 15 percent of Japanese people with moyamoya disease have one or more family members with the condition, indicating that the condition can be passed through generations in families; however, the inheritance pattern is unknown. Research suggests that the condition follows an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. However, some people who have a copy of the altered gene never develop the condition, which is a situation known as reduced penetrance.

Where can I find information about diagnosis or management of moyamoya disease?

These resources address the diagnosis or management of moyamoya disease and may include treatment providers.

You might also find information on the diagnosis or management of moyamoya disease inEducational resources and Patient support.

General information about the diagnosis and management of genetic conditions is available in the Handbook. Read more about genetic testing, particularly the difference between clinical tests and research tests.

To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.

Where can I find additional information about moyamoya disease?

You may find the following resources about moyamoya disease helpful. These materials are written for the general public.

MedlinePlus - Health information (6 links)
Genetic and Rare Diseases Information Center - Information about genetic conditions and rare diseases
Educational resources - Information pages (7 links)
Patient support - For patients and families (3 links)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

Genetic Testing Registry - Repository of genetic test information (4 links)
ClinicalTrials.gov - Linking patients to medical research
PubMed - Recent literature
OMIM - Genetic disorder catalog (4 links)

What other names do people use for moyamoya disease?

cerebrovascular moyamoya disease
moya-moya disease
progressive intracranial arterial occlusion
progressive intracranial occlusive arteropathy
spontaneous occlusion of the Circle of Willis

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines and How are genetic conditions and genes named? in the Handbook.

What if I still have specific questions about moyamoya disease?

Ask the Genetic and Rare Diseases Information Center

Where can I find general information about genetic conditions?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding moyamoya disease?

acids ; angiogenesis ; arteries ; autosomal ; autosomal dominant ; cell ; chorea ; gene ; genetics ;hemorrhage ; infection ; inflammation ; inheritance ; inheritance pattern ; involuntary ; occlusion ;oxygen ; penetrance ; protein ; spontaneous ; syndrome ; tissue ; transient

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

References (8 links)

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook