What is Parkinson’s disease? Parkinson’s disease (PD) is a degenerative disease of the central nervous system, first described in 1817 by the English physician JAMES PARKINSON in a paper he published called “the shaking palsy”, in which he summarized the main symptoms of the disease, which was named after him. Studies have found that the disease currently affects at least 500,000 people in the United States, and some estimates may be higher. Society as a whole pays a huge price for Parkinson’s disease. PD tends to be more prevalent with age, so experts estimate that as society ages, the financial cost of the disease and its impact on human health will gradually increase. What is PD? It is a movement disorder with four main symptoms: tremor (or trembling) of the hands, arms, lower limbs, jaw and head; stiffness (or rigidity) of the limbs and trunk; bradykinesia (or slow movement); and postural instability (or balance disorder). These symptoms often worsen progressively, and as they become more pronounced, patients often have difficulty walking, speaking, and performing other simple movements well. Because other diseases can sometimes cause these symptoms, not all patients with these symptoms have Parkinson’s disease. Parkinson’s disease can be either chronic (i.e., it may last a long time without change) or progressive (i.e., symptoms develop and worsen over time). The disease is not contagious. Although some cases appear to have a genetic predisposition, and some may be traced to specific genetic mutations, the vast majority of cases are disseminated, meaning that the disease is not familially distributed. Many researchers now believe that Parkinson’s disease is the result of a combination of genetic susceptibility and exposure to multiple environmental triggers. It is the most common of the Parkinson’s syndromes, a group of diseases with similar characteristics and symptoms to PD, also known as primary or idiopathic Parkinson’s syndrome, with the term idiopathic implying a group of diseases of unknown cause. There are many known causes, suspected causes, or symptoms from other diseases that can cause Parkinson’s disease, but most cases are non-specific. For example, changes in the blood vessels of the brain can lead to Parkinson’s syndrome.