They will also still pass one mutated copy of the gene on to each of their biological children. As a major surgery the transplant procedure itself also carries standard risks, although the odds of its success are greatly elevated when the only indication for it is an inborn error of metabolism. In absence of a liver transplant, the MSUD diet must be adhered to strictly and permanently. However, in both treatment scenarios, with proper management, those affected are able to live healthy, normal lives without experiencing the severe neurological damage associated with the disease. Pregnancy
Control of metabolism is vital during pregnancy of women with MSUD. To prevent detrimental abnormalities in development of the embryo or fetus, dietary adjustments should be made and plasma amino acid concentrations of the mother should be observed carefully and frequently. Amino acid deficiency can be detected through fetal growth, making it essential to monitor development closely. Prognosis
If left untreated, MSUD will lead to death due to central neurological function failure and respiratory failure. Early detection, diet low in branched-chain amino acids, and close monitoring of blood chemistry can lead to a good prognosis with little or no abnormal developments. Average intellectual development is below that of the general population and the severity of the deficit is a related to the time the condition remained undiagnosed and the effectiveness of dietary control including during metabolic crises. Epidemiology
Maple syrup urine disease (MSUD) is a rare, inherited metabolic disorder.
The majority of children with intermediate MSUD are diagnosed between the ages of 5 months and 7 years. Symptoms associated with classic MSUD also appear in intermediate MSUD. Intermittent MSUD
Contrary to classic and intermediate MSUD, intermittent MSUD individuals will have normal growth and intellectual development. Symptoms of lethargy and characterized odor of maple syrup will occur when the individual experiences stress, does not eat, or develops an infection. Metabolic crisis leading to seizures, coma, and brain damage is still a possibility. Thiamine-response MSUD
Symptoms associated with thiamine-response MSUD are similar to intermediate MSUD. Newborns rarely present with symptoms. Later onset
The symptoms of MSUD may also present later depending on the severity of the disease. Untreated in older individuals, and during times of metabolic crisis, symptoms of the condition include uncharacteristically inappropriate, extreme or erratic behaviour and moods, hallucinations, lack of appetite, weight loss, anemia, diarrhea, vomiting, dehydration, lethargy, oscillating hypertonia and hypotonia, ataxia, seizures, hypoglycaemia, ketoacidosis, opisthotonus, pancreatitis, rapid neurological decline, and coma. Death from cerebral edema will likely occur if there is no treatment. Additionally, MSUD patients experience an abnormal course of diseases in simple infections that can lead to permanent damage. Causes
Mutations in the following genes cause maple syrup urine disease:

BCKDHA (OMIM: 608348)
BCKDHB (OMIM: 248611)
DBT (OMIM: 248610)
DLD (OMIM: 238331)These four genes produce proteins that work together as the branched-chain alpha-keto acid dehydrogenase complex. The complex is essential for breaking down the amino acids leucine, isoleucine, and valine.