This report describes general characteristics of the group of diseases classified as Parkinson disease (PD). Parkinson disease is a genetically heterogeneous disorder, with multiple genes and mapped loci. A comprehensive list of PD subtypes, as defined by OMIM, can be found by following the link in the "OMIM phenotypic series" section, below. A subset of these are listed in the table below, with links to more detailed reports for subtypes that have been investigated using fly models.
[updated Dec. 2016 by FlyBase; FBrf0222196]
Parkinson disease is described as early-onset disease if signs and symptoms begin before age 50. Early-onset cases that begin before age 20 may be referred to as juvenile-onset disease. [from Genetics Home Reference, GHR_condition:parkinson-disease, 2015.02.13]
Parkinson disease (PD) is a neurodegenerative disease usually typified by slow onset in mid to late adulthood; there are also early-onset and juvenile forms of the disease. Symptoms worsen over time and include resting tremor, muscular rigidity, bradykinesia [abnormal slowness of movement], and postural instability [impaired balance and coordination]; additional symptoms may include postural abnormalities, dysautonomia [symptoms caused by malfunction of the autonomic nervous system], dystonic cramps, and dementia. Parkinson disease is the second-most common neurodegenerative disease (after Alzheimer disease), affecting approximately 1% of the population over 50 (Polymeropoulos et al., 1996, pubmed:8895469). [from MIM:168600; 2013.07.23]
Approximately 15% of Parkinson cases appear to be due to an inherited genetic defect. [from Genetics Home Reference, GHR_condition:parkinson-disease, 2015.02.13]
Parkinson disease is a genetically heterogeneous disorder: multiple causative genes have been identified; other genes may confer susceptibility to the disease. Some familial forms are inherited as autosomal dominants, others as autosomal recessives. [from MIM:168600; 2013.07.23]
Although the majority of idiopathic cases of Parkinson disease have Lewy body pathology at autopsy, this feature is not exclusive to Parkinson disease, nor is it observed in all cases.
Pathologic features of classic Parkinson disease include a loss of dopaminergic neurons in the substantia nigra (SN) region of the brain and the presence of Lewy bodies (eosinophilic intracellular inclusions) in surviving neurons in various areas of the brain, particularly the SN (Nussbaum and Polymeropoulos, 1997, pubmed:9300660). [from MIM:168600 and MIM:168601; 2013.07.23]
See diagramatic summary in Trinh and Farrer, 2013, FBrf0226112, pubmed:23857047; http://www.nature.com/nrneurol/journal/v9/n8/fig_tab/nrneurol.2013.132_F1.html.
See descriptive summary for Parkinson's disease in KEGG Disease Pathways (link below).
Current treatment for Parkinson disease remains primarily a dopamine-replacement strategy: the administration of the dopamine precursor, levodopa.
Dysfunction in aspects of synaptic transmission and endosomal trafficking appear to be key processes affected in late-onset PD. Pathways that relate to mitochondrial metabolism are recurring themes for genes associated with early onset PD.
Impaired response to oxidative stress is a recurring theme among the different subtypes of Parkinson disease. Even in familial forms of the disease, despite the fact that all cells carry the same defect and the gene in quesion may be widely expressed, damage reaches a pathologic level in only a few types of cells. While many brain neurons can cope with a rise in oxidative stress, there are select populations of neurons in the brain that are vulnerable; the set of dopaminergic neurons affected in Parkinson disease are among those that are particularly sensitive (Wang and Michaelis, 2010, FBrf0228585).
