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    Parkinson’s disease is a neurodegenerative disorder that affects a part
in the brain called substansia nigra, by the reduction of dopamine in the
brain; leading to movement problems. While Parkinson’s disease was known as
“shaking palsy” since about 175 AD, it was only until 1817 where doctor James
Parkinson gave a detailed essay explaining the shaking palsy (
,2012). Rewarding to his efforts, the medical disease became recognized as
Parkinson’s disease. Parkinson’s disease is both known as a result of genetic
as well as some environmental factors. The former along with the latter
combined together are the factors of most cases of Parkinson’s disease. About
15 percent of the people with PD have inherited it from their ancestors with
this disease (NIH, 2018). Five genes are found to be commonly linked to
Parkinson’s disease. Two genes are inherited as an autosomal dominant, and the
other three genes are inherited as an autosomal recessive. About 1 percent of
people over the age of 60 and 4 percent over the age of 85 are found to have PD
(Pankratz& Foroud, 2007). PD is the second most common neurodegenerative
disorder that can affect the movement, balance, speech, and speed of a person.


  Parkinson’s disease affects the movement of
some parts of the body, especially the limbs. A mutation in some genes can
affect certain nerve cells located in the brain. These nerve cells are located
in a specific place in the brain called Substansia nigra, where a chemical
called dopamine is produced. Dopamine helps control movement by sending signals
to the substansia nigra. Unfortunately, with PD nerve cells would break down
and this will decrease the production of dopamine. Similarly, both environmental factors and genetic disorders together may
cause Parkinson’s disease (PD). Since Parkinson’s disease is very complex, much
research and studies are trying to identify the main cause of it. Evidence has
shown that environmental factors such as pesticides, which are referred to as
endocrine disruptors, increase the risk of PD (NIEHS, 2014). 

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   Genetically, Parkinson’s disease may be
inherited from ancestors or sporadic which can be caused from some
environmental factors that alter or mutate specific genes. Although most cases
appear to be sporadic, in most common cases five genes were found to be
responsible for PD, but some genes are autosomal dominant while others are
autosomal recessive. Mutations in these two genes, SNCA and LRRK2 are
considered autosomal dominant, while Parkin, PINK1, and DJ-1 gene
mutations are considered to be autosomal recessive (Klein & Westenberger,
2012). Disorders in autosomal dominant means that only one mutated allele of
the gene could cause PD, and therefore the individual would pass the mutant
gene to half of his or her children. Disorders in autosomal recessive means
that two mutations either homozygous or heterozygous, one on each allele would
have to be present in order to cause the phenotype. People who are autosomal
recessive and heterozygous for PD are phenotypically unaffected.


five genes that are associated with PD helps acknowledge the disease more and
also helps in the development of new therapies. 
The gene SNCA synthesizes a protein called alpha-synuclein, which is
still being researched on what role it has on the brain. Although it has been
found that this protein forms clumps called lewy bodies in the brain only in
people who suffer from PD. Lewy bodies are abnormal cluster of protein that
grow and spread inside the substansia nigra. Additionally, the genes Pink1, Parkin,
and DJ-1 are proteins that are linked to the regulation of the mitochondria. In
three of those genes, mutations can cause the mitochondria to become abnormal
and unable to function properly. The gene LRRK2 (leucine-rich repeat kinase) is
the most frequently mutated PD gene and the major cause of PD. Mutation of this
gene has been estimated worldwide in about 5% of patients with sporadic PD and
about 20% with hereditary PD (Mullin, Schapira, 2015).


   Furthermore, LRRK2 makes the protein
dardarin which is large and highly conservative. The most common mutation is
the G2019S. Mutations in that gene has been found in patients of PD in the
later-onset of the disease. This gene is found on human chromosome 12. It is
one large polypeptide that functions as an enzyme for two functions, kinase and
GTPase, which both function as signaling molecules. The main role of LRKK2 is
to make sure mitochondria is distributed well in neurons. Mutations in LRRK2
genes may affect the function of the cytoskeleton and protein synthesis as well
as neural damage. The increased activity of the kinase lowers the activity of
the GTPase and therefore can play a vital role in the neural loss in the brain
(Thaler A et. al, 2009).


   One way to know if someone has PD is by
looking at their symptoms. Primary symptoms of PD are tremor, slowed movement,
stiff muscles, impaired balance, and speech changes (Mayo Clinic, 2015). Tremor
is considered to be the main symptom, and it is the shakiness of a certain part
of the body when it is at rest, and usually begins in a limb like the hand. Additionally,
PD patients may also have slower movement abilities, and that relates to the
stiffness of the muscles. Also, speech can be mumbled or slurred and in some
ways where it can be hard for others to understand quickly. Other secondary
symptoms such as memory loss, depression, stress can also be caused by PD.


   Furthermore, currently Parkinson’s disease has
no cure, but there are treatments that help reduce the symptoms of PD and helps
with the motor disturbances. Symptoms such as tremor and slowed movement is
caused by low dopamine levels in the brain. In order to reduce these symptoms,
medications such as Levodopa, which is considered the most common drug for PD
and a natural chemical, is usually given to the patients. When Levodopa enters
the body, it is then converted to dopamine. This medication usually helps with
movement problems. Another medication usually prescribed to PD patients is
Carbidopa. Carbidopa is usually taken in order to make sure that levodopa
doesn’t get damaged before reaching the brain (MedlinePlus, 2015). This
medication is more effective for an early-onset disease. Since no specific
procedure exists to diagnose PD, the disease will be diagnosed based on the
symptoms faced by the patient. Other therapies might also be considered as a
treatment for PD such as healthy eating, exercise, which can strengthen the
muscles and balance.


Conclusively, Parkinson’s
disease is known as an idiopathic disease because the cause of the disease is
yet unknown. Although the symptoms are known, and can be identified as PD
symptoms. The genetic mutations and some environmental factors are identified to
be related to PD and are considered as risk factors for this disease, but not
necessarily the main cause of it. Diagnostic studies may include clinical
diagnosis, MRI scans, and psychological testing. Men are more likely to develop
PD than women, and 1 in every 800 people is likely to develop PD (Gillies et.
al, 2014). Medication is given in order to slow the process of PD, but not stop
it. Research is still proceeding, and the genetic and environmental factors are
used as clues to help find the main cause of Parkinson’s disease.






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