Genetics

Despite considerable progress in understanding the clinical and pathologic features of Parkinson’s disease (PD), the etiology of this condition is still unknown, and the medical and surgical therapies provide only symptomatic relief (1,2). Current working hypotheses are based on two major plausible explanations, the environmental and the genetic hypotheses (3). The scope of environmental factors on causation of PD is discussed in chapter 16. The genetic hypothesis, which gained popularity in the 1990s, stemmed from considerable progress in the development of new molecular genetic techniques and from the description of several large families with a parkinsonian phenotype in many cases closely resembling that of sporadic PD (4-6). However, genetic factors still do not explain the etiology of all cases of PD (7). Thus, a combination of environmental and inherited risk factors may play a crucial role in the development of disease in most cases of parkinsonism.