Maple Syrup Urine Disease
Maple syrup urine disease (MSUD) is a rare inherited disorder in which the body cannot break down certain proteins. MSUD is an amino acid (AA) disorder which occurs when enzymes do not work correctly. As with other AA disorders, maple syrup urine disease affects females and males. It’s estimated that 1 in every 200,000 children born in the United States has maple syrup urine disease.
The most common form of MSUD occurs when a group of enzymes called branched-chain ketoacid dehydrogenase (BCKAD) is missing. This enzyme works to break down the amino acids valine, isoleucine, and leucine. When the body cannot break them down, they build up in the blood.
Symptoms and Complications
There are several forms of MSUD, but the most common — classic MSUD — may be life-threatening. Milder forms of the disease are even less common than the already rare classic form.
Babies with MSUD begin showing symptoms as soon as they ingest protein, which is usually soon after birth. The first symptoms of the disease include:
Babies with the disease also have metabolic crisis episodes that come with irritability, extreme sleepiness, vomiting, and sluggishness. A metabolic crisis usually happens during an illness, stressful events, or after going too long without eating.
If the disease is not treated, it can lead to muscle tone problems, swelling of the brain, metabolic acidosis (high levels of blood acidity), seizures, coma, and possibly death. The disease can also lead to intellectual disabilities, blindness, and brain damage.
While quick and lifelong treatment can give children with MSUD a healthy life with normal development and growth, kids with MSUD are at a higher risk of anxiety, depression, brain swelling, and metabolic crisis.
Testing or Maple Syrup Urine Disease
Maple syrup urine disease is inherited when a child inherits one non-working gene from the mother and father. Most parents of children with MSUD do not have the disease but are carriers of a single defective gene. When both parents are carriers, each pregnancy has a 25% chance of producing a child with MSUD. There is also a 50% chance the child will be a carrier for MSUD and a 25% chance the child will inherit two working copies of the gene.
If you are worried you may be a carrier for MSUD or you have a family history of the disease, Carrier DNA tests for Maple Syrup Urine Disease is available via a blood sample to look for a defective copy of the gene that causes MSUD. If you are a carrier for MSUD, other family members may also be carriers. Siblings of someone with a defective copy of the gene have a 50% chance of being a carrier as well.