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Other forms of dementia

This section of our website presents the results of the Alzheimer Europe project “Rare forms of dementia” which was financed in the framework of the rare diseases programme of the European Commission.

Rare diseases are described by the European Community Action programme as diseases of low prevalence “which is generally recognised as less than 5 per 10,000 in the Community”

While quite extensive work has been carried out on the prevalence of dementia, the same cannot be said for the various forms of dementia, which are covered in this report and for which epidemiological data are often either incomplete or missing. This presented us with an obvious problem at the outset of our project, in order to decide on which forms of dementia we should include and which fulfilled the criteria set out by the European Commission.

It is clear that dementia in itself is not a rare phenomenon under the Commission definition and neither are the two most frequent causes of dementia, Alzheimer’s disease or vascular disease. It it is far more difficult to find a breakdown of the various diseases covered by the definition of dementia. Often the percentages used vary quite considerable.

Alzheimer’s disease is considered to be the main cause of dementia and according to research, should amount to between 50 and 75% of all cases. Vascular dementia is the second most common form of dementia and it is generally accepted that it accounts for between 25 and 50% of all cases of dementia.

For the purpose of our report, we have therefore concluded that all other forms of dementia account for maximum 25% of all forms of dementia, which would give us a prevalence rate of 31.25 per 10,000.

Fronto-temporal degeneration and Lewy body diseases would be the commonest of these rarer forms of dementia and it is generally accepted that they account each for about 5% of all cases of dementia or 7.81 per 10,000. Both of these categories though cannot be considered as one single disease, but rather as a spectrum of different diseases, which would individually fall under the Commission definition of “rare diseases”

Similarly, all other causes of dementia are even rarer and have been included in our report, as well as the rare forms of both Alzheimer’s disease and vascular dementia.

We found some 30 diseases or disease groups which are either rare in themselves or which lead to dementia in rare cases. For each disease we provide general outline, describe the symptoms and course, the causes and risk factors, the genetics, the frequency, the diagnostic procedures, as well as information on care and treatment, ongoing research and available services.

The expert group discussed possible ways on how to present these diseases and we ultimately opted for a classification system based on the causes of dementia, as this system had the advantage of grouping related diseases.

The biggest group of diseases is made up of degenerative diseases , which are characterised by a progressive loss of nerve cells and synapses. For most of these diseases, the causes of this nerve loss are unknown and our knowledge about possible treatment or prevention remains limited.

Infectious diseases are caused by an infectious agent, such as a virus or prion.

Metabolic diseases are a group of often treatable diseases which may lead to dementia and which are caused by an under-activity or over-activity of a part of the human metabolism.

Traumatic diseases are caused by a trauma and in the disease described in this report by repeated head trauma.

Toxic diseases are caused by the consumption of substances, which are harmful to the human body.

Cerebrovascular diseases are diseases of the blood vessels in the brain, which are the second most common cause for dementia.

When describing the various diseases, we have attempted to be as complete as possible, yet we also noted that for a lay reader some information may be too technical or that repetitions between various diseases would have become necessary.

For these reasons, the expert group decided to include some introductory chapters to the disease definitions.

In the introduction, Clive EVERS highlights the importance of dedicating a report to rare forms of dementia and reminds us of the very special needs and expectations of people suffering from rare forms of dementia and their carers.

In the chapter on “Dementia”, Alexander KURZ reminds us that dementia is not a disease, but rather a syndrome which can be caused by a number of various diseases and provides a definition of dementia that is useful for the understanding of the following chapters.

The chapter on “The human brain” by André DELACOURTE gives an overview of how the brain functions and provides some information to link the apparition of symptoms to the areas of the brain which are affected.

To help us understand the information on diagnosis in the disease descriptions, Giuliano BINETTI has dedicated the chapter on “Diagnostic procedures” to an explanation of the various tools that doctors use to come to an accurate and differential diagnosis.

Similarly, the chapter on “Genetics of dementia” by Jos van der POEL is aimed at helping the reader to understand the information on genetics for the various diseases described by describing the various forms of transmission of genetic diseases. At the same time, she raises some of the ethical points involved in genetic testing.

In the final introductory chapter on “Care and treatment”, Clive EVERS addresses the impact of a diagnosis of dementia on a person and his/her family and highlights some of the care and treatment approaches which are relevant to the great majority of rare dementias covered in this report.

On behalf of Alzheimer Europe, I wanted to thank the above-mentioned experts for their contributions, as well as Sandrine LAVALLE, the Communication Officer for the co-ordination and support of the work carried out in the framework of the project and hope that the collected information will prove useful to all people interested in the rarer forms of dementia.

Jean Georges
Executive Director


Last Updated: Thursday 27 August 2015


  • Acknowledgements

    This information was gathered in the framework of the European Commission financed project "Rare forms of dementia". Neither the European Commission nor any person acting on its behalf is responsible for any use that might be made of the following information.
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