Genetisches Testen auf erbliche Parkinson-Syndrome

Although Parkinsons disease (PD) was considered to be a textbook example of a non-genetic condition until the mid 1990s, at least 8 forms of monogenic parkinsonism have been identified in the past 15 years that can be clinically indistinguishable from idiopathic Parkinsons disease. Whereas the currently known PD gene collectively explains only about 5% of all PD cases in Germany, about 5000 of the 100000 German PD patients will have a genetic cause underlying their disease. Major technical advances have been paralleled by a decrease in costs for genetic testing; thus, molecular genetic tests for all known PD genes are offered by certified laboratories in Germany. There are no guidelines for genetic testing for PD; a genetic test should be considered in cases of an early age of disease onset, a specific ethnic background and a positive family history. A careful description of the phenomenology and the putative mode of inheritance is the first step in the diagnosis of a specific form of (hereditary) parkinsonism and the basis for an informed step-wise analysis. A negative test result does not exclude a genetic form. Molecular testing for genetic parkinsonism should be considered in carefully selected cases and may have an important impact on patients despite the current lack of a specific or neuroprotective therapy. This may affect diagnostic procedures, prognostic considerations, family and career planning and even therapeutic approaches. However, a profound change in our view of the role of genetic testing for PD will depend on the advent of neuroprotective therapies.