What is hereditary

GENETIC DEFECTS: WHAT IS HEREDITIVE?

"You got that from your father." This sentence is used more often in some families - not only when it comes to character, but also when it comes to illnesses. "Hereditary disease means that there is a change in our genome, a mutation," explains Prof. André Fischer from the German Center for Neurodegenerative Diseases in Göttingen. This leads to a malfunction in the cells. Prof. Andreas Fritsche prefers to speak of predisposition instead of hereditary diseases. "An inherited disease is often associated with guilt, but that has nothing to do with it," says the deputy head of the Institute for Diabetes Research in Tübingen.

In medicine, a distinction is made between monogenic diseases, in which only one gene is changed, and complex genetic diseases. With the former, the person affected is very likely to fall ill. It is different with complex genetic diseases: "Here every single gene has only a small risk influence, how they interact is still the subject of research," explains Prof. Peter Lichter, Head of the Molecular Genetics Department at the German Cancer Research Center in Heidelberg. Most common diseases such as Alzheimer's, diabetes, cancer or diseases of the cardiovascular system fall into this category. Most of the time it is not just genes that trigger a disease, environmental influences and lifestyle also play an important role. Take Alzheimer's dementia, for example: It is an inherited form. Fischer compares the genome with a library, while different books and chapters correspond to the genes. Every cell needs to know which book and which chapter to open in order to function.

In some cases of Alzheimer's disease such a book is broken, the gene mutates. Then it inevitably leads to Alzheimer's dementia. “It starts relatively early, usually at the age of 40,” says Fischer. However, this form is very rare. "If the father or mother has it, the probability is very high that the next generation will inherit it," explains Fischer. Then a genetic test would be appropriate for security. In the other 99.9 percent who do not have this genetic defect, the disease proceeds in the same way, it only starts later. They also have certain changes in the genetic make-up that pose a certain risk, but alone do not necessarily lead to the onset of the disease. The "second hit" has to be added, i.e. other factors that are usually environmental - such as obesity, diabetes or a high cholesterol level. "So there is not one trigger, but a lot," explains Fischer.

Cancer is hereditary in about five percent of cases, as Lichter points out. For example, if breast cancer occurs in two consecutive generations, i.e. in mother and daughter, there is a high familial risk. If someone falls ill very early, around their late twenties, this is another indication. "Then it is important for the relatives to go to genetic counseling," recommends Lichter. In contrast, there is generally no association between the father's prostate cancer and the daughter's breast cancer.

According to Fritsche, we know of around 300 genetic changes that cause type 2 diabetes: "But they only explain a maximum of one fifth of the disease." Type 2 diabetes is more common, 95 percent of all diabetes patients are affected, as Fritsche explains. "When mother or father are ill, half of all children have diabetes," reports the head of the diabetes ward and diabetes outpatient clinic at the Tübingen University Hospital. If first-degree relatives, i.e. father, mother, siblings are affected, you should see a doctor regularly because there is a high risk, warns Fritsche. However, here too there is an interplay of genetics, lifestyle and the environment. Little exercise or an unhealthy diet accelerate the course of the disease. Type 1 diabetes, on the other hand, usually occurs in families in which no one else has diabetes; heredity is much lower here.

So what should you do if you are genetically predisposed? "You can test the genetic risk," says Fischer. If there is a family history, the costs will be covered by the health insurances. But even if the risk is there, that doesn't mean you actually get Alzheimer's, for example. Nevertheless, those affected could see it as an incentive to do something. "Don't panic under any circumstances," warns Fischer. Because such a test has a psychological component, as the doctors emphasize. "Some say they don't want to know because there is nothing you can do," said Fischer. However, that is not true. The therapies often failed because they were started too late. If genetic counseling reveals a risk, in the case of breast cancer, close monitoring would be initiated, i.e. closely timed imaging examinations, explains Lichter. "Because the earlier the diagnosis, the greater the chances of recovery." If you don't know of any family history, normal preventive care is completely sufficient. Fritsche also warns against activism: "A genetic analysis makes no sense as a general measure."

Source: dpa