22 Interesting Facts About Maple Syrup Urine Disease

Here Are the Top 22 Interesting Facts About Maple Syrup Urine Disease (MSUD):

#1 Maple syrup urine disease, also referred to as branched-chain ketoaciduria, is an inherited disorder in which the human body is unable to process correctly certain amino acids.

#2 It is characterized by poor feeding, vomiting, lethargy, and a maple syrup odor in the cerumen noted soon after birth.

#3 The characteristic odor resembling maple syrup is due to the accumulation of metabolites in the urine.

#4 It was first reported in 1954 by J. H. Menkes and his colleagues.


Classic MSUD

#5 It is the most common form of branched-chain ketoaciduria. Maple syrup odor in cerumen (a yellowish waxy substance) is the first clinical sign of the condition and is present 12-24 hours after birth. If left untreated, it is followed by central respiratory failure and progressive encephalopathy. Onset is commonly triggered when the infant’s body starts to process protein from feedings.

Intermediate MSUD

#6 It is typically diagnosed between the ages of 5 months and 7 years. Individuals with this type of MSUD have 3 to 8 percent of the normal amount of BCKAD enzyme activity. It is characterized by persistently raised branched-chain amino acids and keto acids, however, fewer or no acute episodes of decompensation.

Intermittent MSUD

#7 Affected children with this form of branched-chain ketoaciduria have intellectual development and normal growth throughout infancy and early childhood. Symptoms may not appear until the 1st or 2nd year of life. The initial reaction to the disease commonly occurs when the patient experiences illness, stress, or an unusual increase in protein.


#8 This form usually occurs later in life with a clinical course similar to intermediate MSUD. According to research, individuals with thiamine-responsive MSUD have around 35 percent of the normal activity of the BCKAD enzyme. Also, this form usually improves with large doses of vitamin B1.


#9 In the US, it occurs at the same rate in females and males (approximately 1 in 185,000 people), according to the National Organization for Rare Disorders.

#10 MSUD occurs much more frequently in the Old Order Mennonite (a branch of the Mennonite tradition) population, with an estimated incidence of 1 in 380 newborns. Also, it occurs in the Ashkenazi Jewish population with an incidence of 1:26,000 births.


#11 Babies with the disorder typically begin showing symptoms shortly after birth. These symptoms include:

  • developmental delays;
  • poor appetite;
  • vomiting;
  • trouble sucking during feeding;
  • irritability;
  • weight loss;
  • tiredness;
  • sleeping longer or more often;
  • urine which smells sweet like maple syrup;
  • high-pitched cry.


#12 If it is not detected, the condition can lead to:

  • lack of blood to the brain;
  • swelling of the brain;
  • seizures;
  • vomiting;
  • irritability;
  • loss of cognitive function;
  • extreme fatigue;
  • hypoglycemia (low blood glucose);
  • severe acidosis.

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#13 It is caused by changes in three different genes: BCKDHB, BCKDHA, and DBT. These genes encode the components of the branched-chain alpha-keto acid dehydrogenase complex, which catalyzes the catabolism of the branched-chain amino acids – isoleucine, leucine, and valine.

#14 As a consequence, the keto acids accumulate in the blood. This accumulation can affect the brain and its functional abilities. If left untreated, it can even lead to progressive neuro-degeneration and encephalopathy (brain damage, disease, or malfunction).

#15 Your risk of having any form of branched-chain ketoaciduria depends on whether your parents are carriers of the condition. If both parents are carriers, their child has a:

  • 25% chance of receiving 1 normal gene from each parent;
  • 50% chance of receiving only 1 defective gene and being a carrier;
  • 25% chance of receiving 2 mutated genes and having branched-chain ketoaciduria.

#16 There are many reproductive options available for couples who are both carriers of the gene, such as sperm or egg donation or adoption.

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#17 The diagnosis is confirmed by measuring the levels of organic acids in the urine and amino acids in the blood.

#18 Newborn screening using tandem mass spectrometry has the potential for early detection allowing early initiation of treatment for branched-chain ketoaciduria.


#19 There is no cure for the disorder. If branched-chain ketoaciduria is diagnosed, treatment should be used as soon as possible to reduce the risk of complications.

#20 Treatment involves both a special diet and frequent testing as well as it requires careful monitoring of blood chemistry. Dialysis through a vein or the belly can be done to reduce the level of abnormal substances in the blood. If signs of a metabolic crisis are present, urgent medical care must be found. Treatment is usually lifelong.

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#21 Treatment also involves a special diet that is low in isoleucine, leucine, and valine. High-protein foods need to be limited, including:

  • meat;
  • cheese;
  • peanut butter;
  • fish;
  • shellfish;
  • poultry;
  • nuts;
  • pulses;
  • eggs;
  • red kidney beans;
  • milk;
  • soybeans;
  • spirulina;
  • sesame seeds;
  • sunflower seeds;
  • pumpkin seeds;
  • lupins seeds.


#22 Carrier screening is the best prevention for MSUD.

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