An aid for parents and interested lay persons in the understanding of medical and related terms encountered during care of children with Maple Syrup Urine Disease.

When a child is diagnosed with maple syrup urine disease( MSUD), parents are confronted with a variety of new experiences. Among the many changes and challenges facing them is a new vocabulary (unless the parents are already involved in the medical field). Definitions of some terms in this glossary include specific explanations of how the terms relate to MSUD. While not all-inclusive, the definitions are believed to be correct at time of publication. Other resources should be consulted to verify accuracy and up-to-date usage of any terms in question. Parents, keep this glossary handy for reference when you read about MSUD or when you hear new terms. May it be a help in understanding your child and his or her care.

A condition in which there is a decrease in alkali in body fluids in relation to the acid content. An accumulation of acid metabolites is present and tissue function may be disturbed, especially the central nervous system. (in MSUD acidosis is caused by the accumulation of organic acids which can cause neurological symptoms.)

Indicating acidosis. (See acidosis.)

ADD (attention deficit disorder) or ADHD (attention deficit hyperactivity disorder):
A syndrome affecting children, adolescents, and, rarely, adults, characterized by learning and behavior disabilities. ADD occurs ten times more often in boys, and may result from genetic factors, biochemical irregularity, or other disorders. Symptoms may be mild or severe and include impairment in perception, memory, motor skills, language, and attention span. Children with ADD may be highly emotional and hyperactive and may need medication and special school programs. Symptoms may subside or disappear with time.

Stage of development between the onset of puberty and adulthood, usually beginning between the ages of 11 and 13 with the appearance of secondary sex characteristics, and terminating at 18 to 20 years of age. During this period the individual undergoes extensive physical, psychological, emotional, and personality changes.

Is produced when the amino acid, isoleucine, is metabolized to its keto acid in individuals with MSUD. Alloisoleucine is not normally found in blood of other individuals.

Amino acids:
Organic compounds which are the basic building blocks of all proteins. They are found in all food protein, as well as in the protein of the human body. Of the approximately 80 found in nature, 20 are necessary for human metabolism and growth. Isoleucine, leucine and valine are essential amino acids.

A procedure in which a small amount of amniotic fluid (the fluid that surrounds the baby in the womb) is removed from the uterus for laboratory analysis. Usually performed between the sixteenth and twentieth weeks of pregnancy, the procedure aids in the diagnosis of fetal abnormalities and genetic defects.

Any constructive metabolic process characterized by the conversion of simple substances (such as amino acids) into the more complex compounds of living matter (like muscle). Anabolism is a building process of the body rather than a breaking down process (catabolism).

The separation of substances into their constituent parts and the determination of the elements present. (The term is frequently used when referring to blood analysis for amino acid levels)

The absence of spontaneous respiration or a temporary cessation of breathing from any cause.

Ataxia or ataxic:
Defective muscular coordinat.ion. A staggering gait and postural imbalance indicate ataxia. (Ataxia is sometimes seen in persons with MSUD when leucine levels are elevated)

Autosomal recessive:
A pattern of inheritance in which a recessive gene is present. A person who carries a recessive gene for MSUD has no symptoms of the disease. However, when two carriers have a child, they have a 252 chance of having affected child with each pregnancy.

Bacterial inhibition assay:
A quick screening test for abnormal compounds or excessive amounts of compounds in the blood. The test is used for screening such diseases as PKU and MSUD using a filter paper technique.

The chemistry of living organisms.

Branched-chain amino acids (BCAA):
The amino acids leucine, isoleucine, and valine, which are three of the essential amino acids.

Branched-chain keto acid dehydrogenase:
The complex that is responsible for metabolizing the branched-chain amino acids (leucine, isoleucine, and valine) into their corresponding keto acids. A defect in one of the components of the complex causes MSUD.

Branched-chain keto acids (BCKA):
Derived from the metabolism of the branched-chain amino acids, BCKA may accumulate in the blood and urine of persons with MSUD. (Branched-chain keto aciduria is another name for MSUD)

Person whose chromosomes carry a recessive gene.

The destructive phase of metabolism - the opposite of anabolism. (In MSUD, a breakdown of muscle tissue into amino acids, usually caused by infection or other stress. Catabolism can cause amino acid levels to rise in persons with MSUD)

Cerebral palsy:
A developmental abnormality of the brain resulting in weakness and incoordination of the limbs. The brain damage may result in spasticity, ataxia, seizures, motor problems, varying degrees of mental retardation, impaired speech, vision, and hearing. Treatment may include speech therapy, braces, drugs, and surgical correction of deformities.

Classic MSUD:
A form of MSUD where little or no enzyme activity is present. Individuals with classic MSUD usually have symptoms within the first few days or week of life. The children with classic MSUD usually have lower tolerance for dietary BCAA than children with variant forms of MSUD.

Cognitive or cognition:
The mental process characterized by knowing, thinking, learning, and judging - such as cognitive development and cognitive psychology.

A state of profound unconsciousness from which the patient cannot be aroused.

Abstract ideas or thoughts that originate, and are held, in the mind.

Sudden, violent, involuntary contractions of a group of muscles.

The identification of a disease or condition by a scientific evaluation of physical signs, symptoms, history, laboratory tests, and procedures.

Process of diffusing blood across a semipermeable membrane to remove toxic materials and to maintain fluid, electrolyte, and acid-base balance. In peritoneal dialysis, the lining of the peritoneal cavity is used as the dialysis membrane. In henodialysis, waste materials or poisons are removed from the blood. (Both methods have been used for critically ill infants with MSUD over the years but have mostly been replaced by the use of TPN. See Total Parenteral Nutrition)

DNA (deoxyribonucleic acid):
The genetic material of nearly all living organisms, which controls heredity and is located in the cell nucleus.

DNPH (dinitrophenythydrazine):
A reagent used in a test to detect keto acids in the urine of persons with MSUD. Also referred to as, 2,4-DNPH. Suitable for home testing.

Dysfunction or dysfunctional:
Terms used to describe the inability to function normally.

Prolonged muscle contractions that may cause twisting and repetitive movements or abnormal posturing. The movements may be in the form of rhythmic jerks. In children the legs are usually affected first. (A possible symptom in untreated MSUD)

Ionized salts in blood, tissue fluids and cells including salts of sodium, potassium, and chlorine. Electrolytes are lost from the body during vomiting and diarrhea.

Any dysfunction of the brain.

A complex protein produced by living cells responsible for chemical reactions in organic matter. Most enzymes are produced in small quantities and cause reactions that take place within the cells. (In MSUD an enzyme, branched chain keto acid dehydrogenase, is absent or inactive)

Relating to or affected with fever, which is an elevated body temperature usually due to an infection.

Flaccid muscles:
Weak, soft, and flabby muscles, lacking normal muscle tone.

Gag chromatography/mass spectrometry:
A special test procedure for the separation and analysis of different substances according to their different affinities for a standard absorbent. The gaseous mixture of the substances is passed through a glass cylinder containing the absorbent and is absorbed to a different extent and leaves a characteristic pigment. The bands of color constitute a chromatograph for analysis.

The surgical creation of an artificial opening into the stomach through the abdominal wall through which tube feeding can be administered. (It has been used in infants with MSUD when reflux was a problem)

The biological unit of genetic material which is carried on a particular place on a chromosome.

Recessive gene:
See autosomal recessive.

Dominant gene:
One that produces observable characteristics in an individual, even in carriers of that gene.

The genetic constitution of an individual or group, as determined by the particular set of genes it possesses. The genetic information which determines a particular characteristic. (Compare to phenotype)

A simple sugar (dextrose); an important source of energy in the body and the sole source of energy for the brain.

Guthrie bacteria inhibition asaay:
A test developed by Dr. Robert Guthrie used to screen for PKU and MSUD. The test detects the abnormal presence of amino acids in the blood.

Consisting of dissimilar elements or parts. The term usually refers to carriers - those having one gene for MSUD and one normal gene.

The infusion of a solution that contains sufficient amino acids, glucose, fatty acids, electrolytes, vitamins, and minerals to sustain life, maintain normal growth and development and provide for tissue repair, either through the intestine or with IV's. (See Total Parenteral Nutrition)

Having a lower alanine level in the body (plasma) than normal or sufficient. Alanine is one of the nonessential amino acids which means that it is made in the body and not required to be eaten in food. (Hypoaraninemia is frequently seen in infants with MSUD)

A less-than-normal amount of glucose in the blood. Treatment involves administering glucose orally or by intravenous solution.

Having poor muscle tone, flaccid muscles.

Refers to the number of times an event occurs. In epidemiology, it is the number of new cases of a disease in a particular period of time. Incidence is often expressed as a ratio in which the number of cases is the numerator and the population at risk is the denominator.

A term referring to any disease or condition that is genetically determined and involves either a single gene mutation (like MSUD), multifactorial inheritance, or a chromosomal aberration. Received from one's ancestors.

Intermediate MSUD:
A variant and less severe form of MSUD than classic MSUD. These persons have more enzyrme activity and may not be affected as severely. Unlike intermittent MSUD, the blood levels of the branched-chain amino acids are usually elevated while on an unrestricted diet. The dietary treatment is usually similar to that of classic MSUD. There seem to be several variations of intermediate MSUD.

Intermittent MSUD:
A mild, variant form of MSUD. The first symptoms may not occur until 12 to 24 months of age, usually triggered by an infection or sudden increase in protein intake. The patient becomes irritable, ataxic, and progressively lethargic with an increase of branched-chain amino acid and branched-chain keto acid in the blood and urine. The maple syrup urine smell can usually be noted during these episodes which are "intermittent" between episodes, levels are normal.

Ion-exchange chromatography:
A type of test used to characterize substances found in the blood and urine.

One of the branched-chain amino acids occurring in dietary proteins. It is essential for proper growth in infants and for nitrogen balance in adults. (It is one of the amino acids affected in MSUD)

IV or intravenous:
Refers to providing fluids by injection (using a syringe) or infusion (for large amount of solutions using a bottle connected with tubing) into a vein.

Keto acids (ketoacids):
Products of amino acid metabolism. (In MSUD the branched chain keto acids are not totally metabolized and accumulate in the blood and urine. High levels cause ketoacidosis)

Produced during fat metabolism and usually found in urine after fasting or insufficient caloric intake.

Keto sticks:
Dipsticks used to detect ketones in urine.

Lethargic or lethargy:
Mental and physical sluggishness; a degree of inactivity and unresponsiveness approaching or verging on the unconscious.

One of the branched-chain amino acids occurring in most dietary proteins and essential for optimal growth in infants and nitrogen equilibrium in adults. (It is one of the amino acids affected in MSUD)

Term refers to a function that is not normal.

Maple syrup urine disease (MSUD):
An inherited metabolic disorder in which an enzyme necessary for the breakdown of the amino acids, valine, leucine, and isoleucine (BCAA), is lacking or not functioning fully. The disease can be recognized by the characteristic maple syrup odor of the urine when these BCAA levels are elevated in the blood and urine. Stress, fever, infection, and the ingestion of excess amounts of BCAA aggravate the condition. Treatment reguires dietary restriction of these amino acids and monitoring blood levels.

Medical food:
A specialized dietary product prescribed by health care givers to help correct deficiencies or defects in metabolism. (MSUD formulas are medical foods)

Metabolic acidosis:
Excess acid in body fluids. (See acidosis)

Metabolic disorder:
A dysfunction that results in a loss of metabolic control in the body.

The sum of all the chemical and physical changes that take place within the body and enable its continued growth and functioning. Inborn errors of metabolism are a group of inherited metabolic diseases caused by the absence or deficiency of specific enzymes essential to the metabolism of basic substances such as amino acids, carbohydrates, vitamins, or essential trace elements. (MSUD is one of these inborn errors)

A substance that takes part in the process of metabolism. Metabolites are either produced during metabolism or are constituents of food taken into the body.

mg/dL or mg%:
Common units for measurements of acid, plasma, or chemical solutions. (For example, mg/dL is commonly used to express the measure of leucine levels of persons with MSUD).
1 dL = 100 mL
1 mg = 0.001 g

Moro reflex:
Also known as "startle reflex" a normal muscle reflex in young infants elicited by a sudden loud noise or by striking a table next to the child, resulting in flexion of legs, an embracing posture of arms, and usually a brief cry.

See maple syrup urine disease.

Organic Acids:
Acids containing one or more carboxyl groups. Amino acids are organic acids.

A change in a gene potentially capable of being transmitted to offspring.

Natural protein:
Protein available from ordinary foods such as breads, dairy products, meats, fruits and vegetables.

A newborn infant up to four to six weeks of age.

The field of medicine that deals with the nervous system and its disorders.

Newborn screening:
The process used to test newborns for diseases that would lead to death, mental retardation, or physical defects. Hypothyroidism, PKU, sickle-cell anemia, and MSUD are the diseases most commonly screened.

Substances that provide nourishment and affect the nutritive and metabolic processes of the body.

A prolonged, severe spasm of the muscles causing the back to arch acutely, the head to bend back on the neck, the heels to bend back on the legs, and the arms and hands to flex rigidly at the joints. (a symptom seen in untreated MSUD)

Administered by any way other than through the mouth, such as through IV's.

The study of the preparation, properties, uses, and actions of drugs.

The physical appearance or makeup of an individual (Compare to genotype)

Any of a large group of naturally occurring, complex, organic, nitrogenous compounds. Each is composed of combinations of amino acids. proteins provide the amino acids essential for growth and repair of human tissue.

Relating to the mental origin of muscular movement, and to the production of voluntary movements.

Denoting or expressible as a quantity or a specific amount.

Tenseness; immovability; stiffness; or inflexibility.

See convulsions.

Sensory motor, sensorimotor, or sensomotor:
Pertaining to both sensory (relating to the input division of the nervous system) and motor (causing motion) nerves.

Two or more children who have both parents in common; a brother or a sister is a sibling.

The process or processes involved in the formation of a complex substance from simpler elements or compounds, as the syntheses of proteins from amino acids. Opposite of decomposition.

Beneficial or pertaining to a treatment.

The treatment of any disease.

Occupational therapy:
Therapeutic use of work, self-care, and play activities to increase independent function, enhance development, and prevent disability.

Physical therapy:
The treatment of disorders with physical agents and methods such as massage, manipulation, therapeutic exercises, cold, heat, hydrotherapy, electrical stimulation, and light, to assist in rehabilitating patients and in restoring normal function following an illness or injury.

A water-soluble, crystalline compound of the B complex vitamin group essential for normal metabolism and for the health of the cardiovascular and nervous systems. (Thiamine is a cofactor for the enzyme responsible for MSUD. There is a thiamine-responsive form of MSUD)

Total Parenteral Nutrition (TPN):
Provision of the total nutritional needs by intravenous route for a patient who is unable to take food orally. (A specially prepared TPN is available for treatment of ill children with MSUD) (See hyperalimentation)

Having a poisonous effect; potentially lethal.

An essential branched-chain amino acid produced in the body by the digestion of proteins. It is needed for optimal growth in infants and for nitrogen equilibrium in adults. (It is one of the amino acids affected in MSUD)

Differing in some characteristic from the class to which it belongs, as a variant of a disease, trait, etc. (There are variant forms of MSUD)

Published by the Maple Syrup Urine Disease Family Support Group Compiled and prepared by Joyce Brubacher, Editor, Maple Syrup Maple Syrup Urine Disease Newsletter


The MSUD Family Support Group is currently funding several research projects and we are proactively looking for researchers interested in developing new treatments or finding a cure for MSUD. Significant funding is necessary if we are to accomplish this goal.
Donate Today Learn More

Subscribe to our mailing list

Signup To Our E-Blast Signup with your email address to receive our e-blast newsletter.