Hereditary cerebral amyloid angiopathy

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Hereditary cerebral amyloid angiopathy is a condition characterized by an abnormal buildup of protein clumps called amyloid deposits in the blood vessels in the brain, causing vascular disease (angiopathy). People with hereditary cerebral amyloid angiopathy often have progressive loss of intellectual function (dementia), stroke, and other neurological problems starting in mid-adulthood. Due to neurological decline, this condition is typically fatal in one's sixties, although there is variation depending on the severity of the signs and symptoms. Most affected individuals die within a decade after signs and symptoms first appear, although some people with the disease have survived longer.

There are many different types of hereditary cerebral amyloid angiopathy. The different types are distinguished by their genetic cause, which determines whether areas of the brain other than blood vessels are affected, and the signs and symptoms that occur. The various types of hereditary cerebral amyloid angiopathy are named after the regions where they were first diagnosed.

The Dutch type of hereditary cerebral amyloid angiopathy is the most common form. Stroke is frequently the first sign of the Dutch type and is fatal in about one third of people who have this condition. Survivors often develop dementia and have recurrent strokes. About half of individuals with the Dutch type who have one or more strokes will have recurrent seizures (epilepsy).

People with the Flemish and Italian types of hereditary cerebral amyloid angiopathy are prone to recurrent strokes and dementia. Individuals with the Piedmont type may have one or more strokes and typically experience impaired movements, numbness or tingling (paresthesias), confusion, or dementia.

The first sign of the Icelandic type of hereditary cerebral amyloid angiopathy is typically a stroke followed by dementia. Strokes associated with the Icelandic type usually occur earlier than the other types, with individuals typically experiencing their first stroke in their twenties or thirties.

Strokes are rare in people with the Arctic type of hereditary cerebral amyloid angiopathy, in which the first sign is usually memory loss that then progresses to severe dementia. Strokes are also uncommon in individuals with the Iowa type. This type is characterized by memory loss, problems with vocabulary and the production of speech, personality changes, and involuntary muscle twitches (myoclonus).

Two types of hereditary cerebral amyloid angiopathy, known as familial British dementia and familial Danish dementia, are characterized by dementia and movement problems. Strokes are uncommon in these types. People with the Danish type also have clouding of the lens of the eyes (cataracts) and deafness.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Variants (also called mutations) in the APP gene are the most common cause of hereditary cerebral amyloid angiopathy. APP gene variants cause the Dutch, Italian, Arctic, Iowa, Flemish, and Piedmont types of this condition. Variants in the CST3 gene cause the Icelandic type. Familial British and Danish dementia are caused by variants in the ITM2B gene.

The APP gene provides instructions for making a protein called amyloid precursor protein. This protein is found in many tissues and organs, including the brain and spinal cord (central nervous system). The precise function of this protein is unknown, but researchers speculate that it may attach (bind) to other proteins on the surface of cells or help cells attach to one another. In the brain, the amyloid precursor protein plays a role in the development and maintenance of nerve cells (neurons).

The CST3 gene provides instructions for making a protein called cystatin C. This protein inhibits the activity of enzymes called cathepsins that cut apart other proteins in order to break them down. Cystatin C is found in biological fluids, such as blood. Its levels are especially high in the fluid that surrounds and protects the brain and spinal cord (the cerebrospinal fluid or CSF).

The ITM2B gene provides instructions for producing a protein that is found in all tissues. The function of the ITM2B protein is unclear. It is thought to play a role in triggering the self-destruction of cells (apoptosis) and keeping cells from growing and dividing too fast or in an uncontrolled way. Additionally, the ITM2B protein may be involved in processing the amyloid precursor protein.

Variants in the APP, CST3, or ITM2B gene lead to the production of proteins that are less stable than normal and that tend to cluster together (aggregate). These aggregated proteins form amyloid deposits that accumulate in certain areas of the brain and in its blood vessels. The amyloid deposits in the brain damage neurons, eventually causing cell death and impairing various parts of the brain. Brain cell loss in people with hereditary cerebral amyloid angiopathy can lead to seizures, movement abnormalities, and other neurological problems. In blood vessels, amyloid deposits replace the muscle fibers and elastic fibers that give the blood vessels flexibility, causing them to become weak and prone to breakage. A break in a blood vessel in the brain causes bleeding in the brain (hemorrhagic stroke), which can lead to brain damage and dementia or be life-threatening.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

Hereditary cerebral amyloid angiopathy caused by mutations in the APP, CST3, or ITM2B gene is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.

There is also a non-hereditary form of cerebral amyloid angiopathy that occurs in people with no history of the disorder in their family. The cause of this form of the condition is unknown. These cases are described as sporadic and are not inherited.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

The prevalence of hereditary cerebral amyloid angiopathy is unknown. The Dutch type is the most common, with over 200 affected individuals reported in the scientific literature.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Cerebral amyloid angiopathy · Very frequent (99-80%)

Amyloid deposition in the walls of leptomeningeal and cortical arteries, arterioles, and less often capillaries and veins of the central nervous system.

Cerebral cortical atrophy · Frequent (79-30%)

Atrophy of the cortex of the cerebrum.

Cerebral hemorrhage · Frequent (79-30%)

Hemorrhage into the parenchyma of the brain.

Dilation of Virchow-Robin spaces · Frequent (79-30%)

Increased dimensions of the Virchow-Robin spaces (also known as perivascular spaces), which surround the walls of vessels as they course from the subarachnoid space through the brain parenchyma. Perivascular spaces are commonly microscopic, and not visible on conventional neuroimaging. This term refers to an increase of size of these spaces such that they are visible on neuroimaging (usually magnetic resonance imaging). The dilatations are regular cavities that always contain a patent artery.

Headache · Frequent (79-30%)

Cephalgia, or pain sensed in various parts of the head, not confined to the area of distribution of any nerve.

Seizure · Frequent (79-30%)

A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

Subarachnoid hemorrhage · Frequent (79-30%)

Hemorrhage occurring between the arachnoid mater and the pia mater.

Progressive neurologic deterioration · Frequent (79-30%)

Other findings in the same source

From: Orphanet

Additional reported features include CSF pleocytosis (Occasional (29-5%)); Cerebral cortical microinfarct (Occasional (29-5%)); Dementia (Occasional (29-5%)); Hyperintensity of cerebral white matter on MRI (Occasional (29-5%)); Increased CSF protein concentration (Occasional (29-5%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Hereditary cerebral amyloid angiopathy is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Hereditary cerebral amyloid angiopathy. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.