Are Brain Haemorrhages Hereditary?
Written by Professor Adrian Parry-Jones
Researcher at The University of Manchester and Consultant Vascular Neurologist at the Manchester Centre for Clinical Neurosciences, Salford Royal NHS Foundation Trust.
Spontaneous bleeding in the brain is responsible for around 1 in 10 strokes and affects around 10,000 people in the UK every year and there are a few different causes for intracerebral haemorrhage which I have broken down below.
In older adults, it is usually due to a problem with the small blood vessels in the brain. Most commonly, this is because these blood vessels have been affected by chronic high blood pressure (to read more about managing your blood pressure click here).
Another common cause, especially in the elderly, is where a protein called ‘amyloid’ builds up in the small blood vessels near the surface of the brain. This is called ‘cerebral amyloid angiopathy’.
In younger people, abnormalities of larger blood vessels may be present. These include arteriovenous malformations and cavernomas:
Arteriovenous malformations (sometimes called AVMs for short) are made up of a knot of abnormal blood vessels fed by a larger artery.
Cavernomas resemble a raspberry and are small blood-filled chambers in the brain.
Typically, people are born with AVMs and cavernomas, but they can occasionally develop later in life.
DNA stored in our genes can have an influence on our health. Sometimes mutations in a single abnormal gene can cause a disease. Examples of this are cystic fibrosis or sickle cell disease.
However, many health problems, such as heart disease and diabetes, are caused by the interplay of multiple genes alongside our environment and lifestyle. It is likely that a great many genes may contribute to risk of brain haemorrhage, but very few cases are down to a mutation in a single gene – which is often what people are thinking of when they ask if brain haemorrhages are hereditary.
The likelihood of this depends very much on the cause:
Cavernomas: The most common example of a hereditary cause of intracerebral haemorrhage is cavernomas, where about 20% of cases are hereditary. These cases are caused by inherited mutations in one of three genes (called CCM 1, 2 and 3). When cavernomas are hereditary, they are often multiple. Genetic testing may be offered in this situation or if there is a relevant family history. Someone with a mutation in one of these genes has a 50% chance of passing it on to their children.
AVMs: The vast majority of AVMs are not hereditary. In rare cases where they are, the most common condition is hereditary haemorrhagic telangiectasia. This causes multiple AVMs in the brain, spinal cord and in many other parts of the body. As well as multiple AVMs, abnormal skin blood vessels called telangiectasia can be seen on the lips, in the mouth and on the fingers and give a clue that this is the underlying cause.
Cerebral amyloid angiopathy: Again, the great majority of cases are not hereditary, but there are rare cases where this is the case. Mutations in a gene called APP can cause onset of severe cerebral amyloid angiopathy at a young age and someone with this mutation will have a 50% chance of passing it on to their children. Variations in another gene called APOE seem to have a much weaker effect. Certain variations (called alleles, specifically the APOEε2 and APOEε4 alleles) can lead to a slightly increased tendency to develop cerebral amyloid angiopathy, for it to develop at a slightly younger age, and for there to be a higher risk of brain haemorrhage.
So to sum up, the great majority of cases of brain haemorrhage are not hereditary but our genes play some role in our risk, just like in heart disease and diabetes. However, depending on the underlying cause and using clues from the history, examination and tests, doctors sometimes order genetic testing if there are signs to indicate this might be possible. However, most of the time, genetic testing is not required.
To read more about Brain Haemorrhages, click here.