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MSUD is a metabolism disorder passed down through families in which a person cannot break down the amino acids leucine, isoleucine and valine.This is caused by a gene defect.
There are several treatment options to assist in lessening the impact on the body. Treatment involves eating a protein free diet, avoiding foods like eggs, meat, fish and nuts. Individuals with MSUD must remain on this diet for their entire life in order to avoid neurological damage. IV is a method used to transfer fluids, sugars and sometimes fats into the patients body. There is also a formula available to cause excess amino acids to be used up within the body, during protein synthesis. Frequent blood tests are necessary to ensure there is no accumulation of amino acids, which would result in neurological damage.
Through consuming a protein free diet, it doesn't add to the protein already built up in the blood, which means there is less amino acids to attempt to break down. Even with following a strict diet, people with MSUD can still experience high levels of leucine during times of physical and emotional stress.
BCKDHA:
BCKDHB:
DBT:
Maple Syrup Urine Disease can have a serious impact on the central nervous system if left untreated. It affects the myelinated white matter of the brain and can lead to dysmyelination, meaning there is destruction or damage to normal myelination. Individuals with MSUD can also experience cerebral edema, a condition where excess fluid accumulates in the intracellular or extracellular spaces of the brain. It is important to treat this disease as early as possible, as it causes brain cells to rapidly degenerate.
The disease develops from a mutation in the DNA, which causes the absense or deficiency in a particular enzyme, BCKAD, that breaks down the amino acid leucine. The development of the affected individual's DNA would would begin during initial cell production, and the since the liver deaminates amino acids, MSUD indirectly impacts the endocrine system.
Infants should be tested as soon as they can following birth, either on the fifth day of their life, being discharged from the hospital, or after death to discover if it was a possible cause of death.
Genetic or DNA testing is available to see if parents carry the recessive allele. A test is done on a blood sample to look for changes in the pair of specific genes that code for MSUD.
The characteristic odor, and unusually high concentrations of keto and amino acids in the urine typically confirm the suspected possibility of the disease being present.
An enzyme test is available to be done on a blood or skin sample.Test for elevated blood leucine, with a filter blood paper specimen. MSUD is tested by the amounts of leucine, with abnormal amounts being greater than 0.4 mg/mL.
The liver is the largest organ in the body, and develops from the mesodermic germ layer. The livers ability to maintain homeostasis within the body is significantly altered with the mutated enzyme present with MSUD. The liver is therefore unable to deaminate amino acids, causing them to accumulate becoming detrimental to the central nervous system and for protein synthesis.
Endocrine processes cause the amino acids to overflow within the body and appear in waste from the body, causing a maple syrup or burnt sugar scent of the urine. Normally, the endocrine system secretes hormones to promote the secretion of enzymes, however, the enzyme required would be deficient and would not complete the required breakdown of the amino acids from protein sources.
Depending on the severity of the disorder, the effects will vary.The main effect of the conditions is that it makes the affected persons urine have a sweet smell, like maple syrup. This is a result of decreased or absent enzyme activity. In more serious cases, people may suffer from brain damage or intellectual disability. Both of these effects are brought on by physical stress.
Maple Syrup Urine Disease manifests itself within an infant during the first 12-24 hours of it being born. Yet, the disease doesnt reveal itself until upwards of 2 weeks after birth. It can maniest itself in different levels of severity but the most common form is associated with the lowest enzyme activity.
A possible treatment option for people with MSUD is liver transplantation. This procedure must be thoroughly discussed with physicians and individuals involved, and it also requires life long medicating to prevent the rejection of the donated liver. Although, successful transplants cure individuals of their MSUD symptoms.
BCKD is a mitochondrial complex that breaks down certain amino acids.
MSUD is caused by mutations in the BCKDHA, BCKDHB, and DBT genes.
Amino acids begin to build up in the body and these mutations prevent the breakdown of isoleucine, leucine, and valine
Life expectancy is determined by the treatment that is recieved. If successfully treated, individuals with MSUD can live a normal life. However, if it is untreated death can happen during infancy.
Reproduction & Development
MSUD can be very difficult to manage with the only treatment being dietary restriction. Interestingly, even following a diet absent of protein, certain common illness can bring on spastic episodes where muscles vary from ridgid to floppy. Stress hormones such as adrenaline and cortisol may play a role in the severity of MSUD, as ongoing research may suggest.
Punnett Squares
R r
r r
r r r
r r r
r r r
r r r
0.00540 individuals have MSUD out of 1000 people in Canada
Infants have a higher frequency of this disease because an individual who has MSUD has a low chance of survival unless they follow a very strict diet. As a result, more babies have it than adults and it is diagnosed at an early age.
R R
r r r
Carrier frequency varies, and is notably higher in certain populations of individuals.
Old order Mennonites in Pennsylvania and derivative settlements have a frequency of 1 in 13^3 for MSUD type 1A.
General population, 1 in 321^1 for MSUD type 1A.
Ashkenazi Jewish population have a 1 in 97^4 for MSUD type 1B.
Giorgi, A. (n.d.). Maple Syrup Urine Disease. Retrieved May 9, 2015, from
http://www.healthline.com/health/maple-syrup-urine-disease
Haldeman, C. (2012, May 12). Maple Syrup Urine Disease. Retrieved Jun 7, 2015, from
http://www.nlm.nih.gov/medlineplus/ency/article/000373.htm
Roberts, N. (2012) Maple Syrup Urine Disease: New Insights from a Zebrafish Model. Retrieved May 15, 2015, from
http://www.ncbi.nlm.nih.gov/PMC/articles/PMS3380704/
Unknown. Diagnostics for MSUD. (2015). Retrieved May 13 2015, from
http://www.uic.edu/classes/phar/phar332/Clinical_Cases/aametabcasese/MSUD/Diagnostics_of_MSUD.html
Unknown. Maple Syrup Urine Disease. (2015,June 8). Retrieved June 8 2015, from
http://ghr.nlm.nih.gov/condition/maple-syrup-urine-disease
Allelic Frequency:
q^2= 0.00540/1000
q= 0.00232
p=1-q
=0.998
Unknown. Maple Syrup Urine Disease (MSUD). (2015). Retrieved June 8 2015, from
http://learn.genetics.utah.edu/content/disorders/singlegene/msud/
Genotype:
rr (q^2)=5.41 X 10^-6
RR (p^2)=0.995
Rr (2pq)=0.00464
Phenotype:
No disease=0.995
Carrier=0.00464
With disease=5.41 X 10^-6