Describe the mode of inheritance (chromosomal error, dominant, recessive, sex-linked, etc). Clearly explain how this disease is inherited using terms you understand.
Autosomal recessive, defective gene on the autosome gene. The disease is inherited usually by two carriers of the disease or a person with the disease and a carrier of the disease. The affected person inherits one non-working gene for MSUD from each parent.
What causes the disorder? Is it a mutation? A genetic tendency triggered by other factors?
MSUD is a metabolic disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), leading to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products (ketoacids) in the blood and urine. MSUD can result from mutations in any of the genes that code for the enzyme subunits. MSUD has a much higher prevalence in children of Amish, Mennonite, and Jewish descent.
If someone has this disease, what are the probable genotypes of the parents? If the disease is a chromosomal abnormality, describe the abnormality. What are the chances of a person with this disease passing the disease to their offspring? (Include possible scenarios)
Mm & Mm, mm & mm, or Mm & mm. The abnormality is that one of the autosome genes inherited is defective. It is only possible for the person with this disease to pass it on to their child if their spouse is heterozygous for the disease or has the disease themselves.
How many people are affected by this disease? What types of people are likely to have the disorder? Is it more common in a certain group of people?
Maple syrup urine disease affects an estimated 1 in 185,000 infants worldwide. The disorder occurs much more frequently in children of Amish, Mennonite, and Jewish descent.
How common is the disease?
Maple syrup urine disease affects an estimated 1 in 185,000 infants worldwide.
How is the disease diagnosed? What tests are done? Is there a prenatal test available? If so, what is it called?
When symptoms become present after the newborn period, diagnosis of MSUD can be made by urine analysis or a blood test. In a child with MSUD, urine analysis will show a high rate of keto acids; a blood test will show a high level of amino acids. The diagnosis of MSUD also can be confirmed with enzyme analysis of white blood cells or skin cells. Data from the National Newborn Screening and Genetics Resource Center (NNSGRC) indicates that every state in the United States tests infants for MSUD as part of their newborn screening program. (NNSGRC, 2011) Newborn diagnosis is made through a blood test that also screens for more than 30 different disorders.
What are the physical symptoms of the disease?
Any common illness or infection can cause elevations in the BCAAs which may precipitate an episode of vomiting, diarrhea, irritability, sleepiness, unusual breathing, staggering, hallucinations, and slurred speech. Left untreated, the child can go into a coma and die. Thus, any signs of illness require initiation of a sick day plan and immediate contact with a health care provider to begin treatment for the illness.
What kind of medical assistance will the affected person need?
Patients with moderate MSUD can live decently as long as their diets are kept strict and regulated with not too much protein and they make sure levels of protein and their metabolic balance is not too unstable. Infants that exhibit life threatening symptoms such as going in to comas or seizures, rare but possible, may have to stay in the hospital for further treatment until their protein levels are normal.
What is the long-term outlook for a person with this disease?
MSUD can be treatable and manageable and if treated properly, but often people with this disease are burdened with the trouble of having to follow a diet so strict they can't eat meat or dairy. People with the disorder can grow into healthy adulthood; however, people or infants with severe MSUD may want to invest in a liver transplant for a healthy liver or frequent dialysis to eliminate some of the protein buildup in their bodies.
What is the life expectancy of someone with the disease?
The average life expectancy of someone with moderate MSUD is normal compared to someone without the disorder, if treated properly. If not, however, infants diagnosed with the disease usually die within the first few weeks after birth.
How can the disease be treated or cured?
A controlled diet that is started immediately after diagnosis is the main focus of treatment for MSUD. Leucine, isolucine, and valine are amino acids that are extremely controlled when being admitted to the diet, as these are the proteins that break down slower and therefore cause the disorder.
What is the current status of research on this disease?
MSUD has been around for years and was first discovered in the 1950s after several newborn infants died quickly after birth and their common symptoms including the maple-syrup scented urine was noticed by researchers. Research continues; however, there aren't many options besides a liver transplant since this disease is inherited at birth in the liver.
Karyotype of MSUD
There is no karyotype available for Maple Syrup Urine Disease because it is not a defect in the chromosome; it is just a defect in one of the alleles.
Pedigree of MSUD
Autosomal recessive, defective gene on the autosome gene. The disease is inherited usually by two carriers of the disease or a person with the disease and a carrier of the disease. The affected person inherits one non-working gene for MSUD from each parent.
What causes the disorder? Is it a mutation? A genetic tendency triggered by other factors?
MSUD is a metabolic disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), leading to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products (ketoacids) in the blood and urine. MSUD can result from mutations in any of the genes that code for the enzyme subunits. MSUD has a much higher prevalence in children of Amish, Mennonite, and Jewish descent.
If someone has this disease, what are the probable genotypes of the parents? If the disease is a chromosomal abnormality, describe the abnormality. What are the chances of a person with this disease passing the disease to their offspring? (Include possible scenarios)
Mm & Mm, mm & mm, or Mm & mm. The abnormality is that one of the autosome genes inherited is defective. It is only possible for the person with this disease to pass it on to their child if their spouse is heterozygous for the disease or has the disease themselves.
How many people are affected by this disease? What types of people are likely to have the disorder? Is it more common in a certain group of people?
Maple syrup urine disease affects an estimated 1 in 185,000 infants worldwide. The disorder occurs much more frequently in children of Amish, Mennonite, and Jewish descent.
How common is the disease?
Maple syrup urine disease affects an estimated 1 in 185,000 infants worldwide.
How is the disease diagnosed? What tests are done? Is there a prenatal test available? If so, what is it called?
When symptoms become present after the newborn period, diagnosis of MSUD can be made by urine analysis or a blood test. In a child with MSUD, urine analysis will show a high rate of keto acids; a blood test will show a high level of amino acids. The diagnosis of MSUD also can be confirmed with enzyme analysis of white blood cells or skin cells. Data from the National Newborn Screening and Genetics Resource Center (NNSGRC) indicates that every state in the United States tests infants for MSUD as part of their newborn screening program. (NNSGRC, 2011) Newborn diagnosis is made through a blood test that also screens for more than 30 different disorders.
What are the physical symptoms of the disease?
Any common illness or infection can cause elevations in the BCAAs which may precipitate an episode of vomiting, diarrhea, irritability, sleepiness, unusual breathing, staggering, hallucinations, and slurred speech. Left untreated, the child can go into a coma and die. Thus, any signs of illness require initiation of a sick day plan and immediate contact with a health care provider to begin treatment for the illness.
What kind of medical assistance will the affected person need?
Patients with moderate MSUD can live decently as long as their diets are kept strict and regulated with not too much protein and they make sure levels of protein and their metabolic balance is not too unstable. Infants that exhibit life threatening symptoms such as going in to comas or seizures, rare but possible, may have to stay in the hospital for further treatment until their protein levels are normal.
What is the long-term outlook for a person with this disease?
MSUD can be treatable and manageable and if treated properly, but often people with this disease are burdened with the trouble of having to follow a diet so strict they can't eat meat or dairy. People with the disorder can grow into healthy adulthood; however, people or infants with severe MSUD may want to invest in a liver transplant for a healthy liver or frequent dialysis to eliminate some of the protein buildup in their bodies.
What is the life expectancy of someone with the disease?
The average life expectancy of someone with moderate MSUD is normal compared to someone without the disorder, if treated properly. If not, however, infants diagnosed with the disease usually die within the first few weeks after birth.
How can the disease be treated or cured?
A controlled diet that is started immediately after diagnosis is the main focus of treatment for MSUD. Leucine, isolucine, and valine are amino acids that are extremely controlled when being admitted to the diet, as these are the proteins that break down slower and therefore cause the disorder.
What is the current status of research on this disease?
MSUD has been around for years and was first discovered in the 1950s after several newborn infants died quickly after birth and their common symptoms including the maple-syrup scented urine was noticed by researchers. Research continues; however, there aren't many options besides a liver transplant since this disease is inherited at birth in the liver.
Karyotype of MSUD
There is no karyotype available for Maple Syrup Urine Disease because it is not a defect in the chromosome; it is just a defect in one of the alleles.
Pedigree of MSUD
This is an image of a baby with MSUD. As you can see in the picture, there are no visible differences apparent to the human eye. It is only small genetic defects that make the disorder clear.
