MedGen

Parkinson disease (PD) was first described by James Parkinson in 1817. It is the second most common neurodegenerative disorder after Alzheimer disease (AD; 104300), affecting approximately 1% of the population over age 50 (Polymeropoulos et al., 1996). Reviews Warner and Schapira (2003) reviewed the genetic and environmental causes of Parkinson disease. Feany (2004) reviewed the genetics of Parkinson disease and provided a speculative model of interactions among proteins implicated in PD. Lees et al. (2009) provided a review of Parkinson disease, with emphasis on diagnosis, neuropathology, and treatment. Genetic Heterogeneity of Parkinson Disease Several loci for autosomal dominant Parkinson disease have been identified, including PARK1 (168601) and PARK4, caused by mutation in or triplication of the alpha-synuclein gene (SNCA; 163890), respectively, on 4q22; PARK5 (191342), caused by mutation in the UCHL1 gene on 4p13; PARK8 (607060), caused by mutation in the LRRK2 gene (609007) on 12q12; PARK11 (607688), caused by mutation in the GIGYF2 gene (612003) on 2q37; PARK13 (610297), caused by mutation in the HTRA2 gene (606441) on 2p13; PARK17 (614203), caused by mutation in the VPS35 gene (601501) on 16q11; PARK18 (614251), caused by mutation in the EIF4G1 gene (600495) on 3q27; PARK22 (616710), caused by mutation in the CHCHD2 gene (616244) on 7p11; PARK24 (619491), caused by mutation in the PSAP gene (176801) on 10q22; and PARK26 (620923), caused by mutation in the RAB32 gene (612906) on chromosome 6q24. Several loci for autosomal recessive early-onset Parkinson disease have been identified: PARK2 (600116), caused by mutation in the gene encoding parkin (PRKN, PARK2; 602544) on 6q26; PARK6 (605909), caused by mutation in the PINK1 gene (608309) on 1p36; PARK7 (606324), caused by mutation in the DJ1 gene (PARK7; 602533) on 1p36; PARK14 (612953), caused by mutation in the PLA2G6 gene (603604) on 22q13; PARK15 (260300), caused by mutation in the FBXO7 gene (605648) on 22q12.3; PARK19A (615528) and PARK19B (see 615528), caused by mutation in the DNAJC6 gene (608375) on 1p31.3; PARK20 (615530), caused by mutation in the SYNJ1 gene (604297) on 21q22; and PARK23 (616840), caused by mutation in the VPS13C gene (608879) on 15q22; and PARK25 (620482), caused by mutation in the PTPA gene (600756) on 9q34. PARK3 (602404) has been mapped to chromosome 2p13; PARK10 (606852) has been mapped to chromosome 1p32; PARK16 (613164) has been mapped to chromosome 1q32. See also PARK21 (616361). A locus on the X chromosome has been identified (PARK12; 300557). There is also evidence that mitochondrial mutations may cause or contribute to Parkinson disease (see 556500). Susceptibility to the development of the more common late-onset form of Parkinson disease has been associated with polymorphisms or mutations in several genes, including GBA (606463), MAPT (157140), MC1R (155555), ADH1C (103730), and genes at the HLA locus (see, e.g., HLA-DRA, 142860). Each of these risk factors independently may have a modest effect on disease development, but together may have a substantial cumulative effect (Hamza et al., 2010). Susceptibility to PD may also be conferred by expanded trinucleotide repeats in several genes causing other neurologic disorders usually characterized by spinocerebellar ataxia (SCA), including the ATXN2 (601517), ATXN3 (607047), TBP (600075), and ATXN8OS (603680) genes. [from OMIM]

A malignant epithelial neoplasm that arises from the colon or rectum and invades through the muscularis mucosa into the submucosa. The vast majority are adenocarcinomas. [from NCI]

Alzheimer's disease is a degenerative disease of the brain that causes dementia, which is a gradual loss of memory, judgment, and ability to function. This disorder usually appears in people older than age 65, but less common forms of the disease appear earlier in adulthood.

Memory loss is the most common sign of Alzheimer's disease. Forgetfulness may be subtle at first, but the loss of memory worsens over time until it interferes with most aspects of daily living. Even in familiar settings, a person with Alzheimer's disease may get lost or become confused. Routine tasks such as preparing meals, doing laundry, and performing other household chores can be challenging. Additionally, it may become difficult to recognize people and name objects. Affected people increasingly require help with dressing, eating, and personal care.

As the disorder progresses, some people with Alzheimer's disease experience personality and behavioral changes and have trouble interacting in a socially appropriate manner. Other common symptoms include agitation, restlessness, withdrawal, and loss of language skills. People with Alzheimer's disease usually require total care during the advanced stages of the disease.

Individuals with Alzheimer's disease usually survive 8 to 10 years after the appearance of symptoms, but the course of the disease can range from 1 to 25 years. Survival is usually shorter in individuals diagnosed after age 80 than in those diagnosed at a younger age. In Alzheimer's disease, death usually results from pneumonia, malnutrition, or general body wasting (inanition).

Alzheimer's disease can be classified as early-onset or late-onset. The signs and symptoms of the early-onset form appear between a person's thirties and mid-sixties, while the late-onset form appears during or after a person's mid-sixties. The early-onset form of Alzheimer's disease is much less common than the late-onset form, accounting for less than 10 percent of all cases of Alzheimer's disease. [from MedlinePlus Genetics]