The Finnish disease heritage (FDH) consists of almost forty rare hereditary diseases that are clearly more prevalent in Finland than elsewhere in the world. These all are particularly rare diseases: the FDH does not include so-called common diseases that are also caused by genes, though only partly (for example cardiovascular diseases). On the other hand, the concept of Finnish disease heritage reversed means that there are many diseases lacking in Finland that are common elsewhere in the world. 

What causes FDH?

The special assortment of rare diseases among Finns is caused by the fact that the population living in Finland today is descended from a relatively small original population. These original settlers of Finland carried a certain random selection of genes. This selection happened to include some genes that are very rare elsewhere and, on the other hand, some other genes are lacking that are relatively common elsewhere. Today’s population is almost entirely made up of the descendents of these original settlers. As the population has increased, some genes have increased even more while others may have disappeared.

As a piece of local colour: There are areas in Finland where the population has moulded during the past few centuries. The migration began in the 1500s when people started moving into the interior part of the country and settled there. This means that in certain parishes today almost everyone may be descended from the few original families. 

What diseases? 
 

The rare diseases composing the FDH cover almost all fields of medicine. They include diseases causing

• mental retardation (for example, Aspartylglucosaminuria or AGU, Infantile neuronal ceroid lipofuscinosisor INCL, and Salla disease)
• growth disturbances (Diastrophic growth disorder, Cartilage-hair hypoplasia and Mulibrey disorder)
• visual impairment (Retinoschisis) or deaf- and blindness (Usher syndrome)
• metabolic disturbances (Nonketotic hyperglycinemia)
• structural abnormalities (Rapadilino)

On the other hand, some hereditary diseases common elsewhere like phenylketonuria and cystic fibrosis are clearly rare in Finland.

The majority of the hereditary diseases existing in Finland are not part of the Finnish disease heritage and their prevalence is the same in Finland as elsewhere. 

How are diseases inherited? 

The majority of the diseases in the FDH are inherited recessively. This means that the disease can appear only if the child has inherited two faulty genes, one from each parent. The parents themselves are healthy as both have only one of these genes. The disease is usually found in only one set of siblings in a kindred, because a carrier of the gene will only very rarely happen to find a spouse carrying the same rare gene. When a child with the disease is born to a family, the risk for each subsequent child to have the same disease is 25%. 

What research is being conducted? 

Research on the clinical progression and treatment of many FDH diseases has been carried out especially in Finland, also gene research on these diseases is very active in Finland. The locality of the disease gene on the chromosome is known all the diseases, and for many the gene itself and its errors are known in detail.

For more on the issue

 
Finnish Disease Database
Finland's Fascinating Genes , an article in the American scientific journal Discover.
Reijo Norio: Genetics and the Origins of the Finns. In: Encyclopedia of Life Sciences. 2008
Reijo Norio: Finnish Disease Heritage I: characteristics, causes, background. Human Genetics Vol. 112(5-6): May 2003.
Reijo Norio: Finnish Disease Heritage II: population prehistory and genetic roots of Finns. Human Genetics Vol. 112(5-6): May 2003.
Reijo Norio: The Finnish Disease Heritage III: the individual diseases. Human Genetics Vol.112(5-6): May 2003.
 

12.10.2011/Lt