MSUD affects the way the body breaks down the three amino acids: leucine, isoleucine, and valine. The disease stops one of the six proteins that is supposed to break down these acids. Since nothing breaks it down, the acids build up and cause brain cells to die and eventually death if left untreated. MSUD is very rare and usually causes babies to die in first 2-3 months of birth. It effects the urine, brain, liver, eyes, and kidneys.

Maple Syrup Urine Disease is Autosomal Recessive, which means both parents each carry one copy of the mutated gene, but usually only carry it and are not infected by MSUD. For the babies of two parents carrying the mutated gene, there is a: 25% chance of being normal, 50% chance of carrying the disease, and a 25% chance of having it.

Symptoms are: loss of appetite, fussiness, sweet-smelling urine, and if the disease worsens, more severe symptoms come into play, such as: seizures, comas, eventually death, and without treatment the baby would die in the first few months of life. Beginning symptoms should show in the first 3-4 days of birth.

Daily Life:

This disease is diagnosed by a possible screening of the baby in the first 24 hours of birth in some places. Or a blood sample could also be taken from the baby’s heel to be analyzed for high leucine levels. If the baby is not checked after birth, the guardians will most likely notice symptoms and bring their baby to a doctor to see what’s happening, there they are diagnosed. To diagnose this disease later in life, most doctors would go down a checklist, and possibly a bloods sample/scan to make sure. Sweet-smelling urine or earwax is a key symptom to diagnosing this disease.

MSUD is treated by restricting the patient from the three amino acids. Treatment must begin very early before any brain damage is done. Patients must eat a special formula that does not contain the amino acids. These diets consist of strict food, no meat, eggs, or nuts. If too much of the three amino acids are taken in, patients are treated with a solution through the vein to use up the amino acids. Future gene therapy can replace the mutated gene with a good copy to break down these three amino acids.

Research for MSUD is progressing. Gene therapy is being conducted to replace the mutated gene with a good one, which would break down the amino acids. A new diet is also being conducted, looking into three omega fatty acids, possibly holding back this disease. New treatments and solutions are being made to extract the amino acids, or too regenerate or smother some of the brain damage done.

Additional Facts:
Only 1 in 180,000 babies are born with MSUD, which is less than .001 percent chance. Mennonites in Pennsylvania have a 1 out of every 176 babies, this is about a 5% chance to have this disease in a certain population. This disease has three severities, so some people can survive for longer; over 30 years. Soon there might be a cure, possibly through gene therapy.

Punnett Square:


Pedigree Chart:


Learn Genetics

Your Guide to Understanding Genetic Conditions

MSUD Family Support Group