Maple Syrup Disease
Done by:
Naser Batel Alrowaily
ID: 401100662
Supervised by:
Dr. Ismaeil Hamad Othman
2020
Maple syrup urine disease
1- Introduction
Maple syrup urine disease (MSUD), It is also called branched chain ketonuria(1) :is an autosomal
recessive disorder described by the interruption of the process of the branched-chain α-ketoacid
dehydrogenase (BCKAD) , which is the second step in the catabolic pathway for the branched-chain
amino acids (BCAAs) that include leucine, isoleucine, and valine. (2). The first step is to convert
leucine, isoleucine, and valine into their relevant α-ketoacids by branch-chain aminotransferase within
the mitochondria (Figure 1). During the second step in BCAA catabolism, the BCKAD complex begins
oxidative decarboxylation of α-ketoacids. This transformation results in the conversion of α-ketoacids
into acetoacetate, acetyl-CoA, and succinyl-CoA as illustrated in Figure 1. (2) In other way, babies
with MSUD can not break down the amino acids (leucine, isoleucine and valine) . As a result, the very
high levels of these amino acids in blood stream and urine are harmful and can lead to MSUD.
Fig1: BCAA catabolic process. The BCAAs undergo transamination that is catalysed by the branched-chain
aminotransferase (BCAT) and requires α- ketoglutarate, leading to the production of the α-ketoacids KIC,
KMV, and KIV. These intermediates then undergo oxidative decarboxylation, catalysed by the BCKAD
complex. Abbreviations: KIC, α-ketoisocaproic acid; KIV, α-ketoisovaleric acid; KMV, α-keto-βmethylvaleric acid; Glu, glutamate; BCAAs, branched-chain amino acids; BCKAD, branched-chain α-ketoacid
dehydrogenase. (2)
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2- Symptoms of maple syrup urine disease
Disease begins at the birth’s first days. It is characterized by convulsions, severe mental
retardation, vomiting, acidosis, coma and can causes death within the first year of life. (1)
More general symptoms include: (2)

sweat and urine smells like maple syrup

poor feeding or loss of appetite

weight loss
Babies have MSUD may also have series of symptoms known as a "metabolic crisis", sometimes
early in their life. Symptoms of a metabolic crisis include: (1)

seizures

lack of energy

vomiting

irritability

breathing difficulties
It's important to get treated immediately as your baby advances symptoms of a metabolic crisis.
In some cases, a metabolic crisis may be triggered later in childhood by an infection or illness. The
hospital will provide you with emergency treatment instructions to follow if your child is ill, which
helps prevent these symptoms developing.(1)
3- Diagnosis:
In MSUD, urine have branched chain keto acids, valine, leucine and isoleucine within it. Diagnosis
is done by analysing enzyme in cells and must be done at the first days of birth.(1)
4- Treatment:
MSUD treated by giving a diet, which is low in branched chain amino acids. This leads to maintain
the amino acids percent low in blood and then preventing the symptoms from being developed. The
following foods must be avoided because the high protein included in it:
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
meat

fish

cheese

eggs

pulses

nuts
Also liver transplantation has been successfully tried in some cases of MSUD. (1)
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References
1-DM VASUDEVAN, Sreekumari S Skannan Vaidyanathan, 2011. Textbook of Biochemistry for
Medical Students. Jaypee brothers medical publishers (p) ltd, sixth edition, ISBN: 9789350250167.
2-Patrick R Blackburn, Jennifer M Gass, Filippo Pinto e Vairo, Kristen M Farnham, Herjot
K Atwal, Sarah Macklin, Eric W Klee, Paldeep S Atwal, 2011. Maple syrup urine
disease: mechanisms and management. The Application of Clinical Genetics. Retrieved
from: https://www.dovepress.com
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