MAPLE SYRUP
URINE DISEASE |
ALTERNATE NAMES
|
MSUD; Branched-Chain Ketoaciduria; Branched-Chain Alpha-Ketoacid Dehydrogenase Deficiency;
BCKD Deficiency
|
DESCRIPTION |
Maple Syrup Urine Disease (MSUD) is an inherited metabolic disorder in which the body
is unable to process certain protein building blocks (amino acids) properly. Because
these amino acids are not metabolized, they, along with their various byproducts,
abnormally accumulate in the cells and fluids of the body. The condition gets its
name from the distinctive sweet odor of the affected infant’s earwax, sweat and urine.
Mutations in the BCKDHA, BCKDHB, DBT and DLD genes cause MSUD. Individuals with this
condition cannot break down the branched chained amino acids leucine, isoleucine,
and valine (BCAA). This leads to a buildup of these chemicals in the blood.
There are four common forms:
-
1.
Classic MSUD. In the classic form, the disorder presents after the infant has had milk containing
protein. This causes an increase in the offending amino acids which become toxic to
the brain. Classic MSUD tends to impair intellectual development and bone growth.
-
2.
Intermediate MSUD. Onset of symptoms of intermediate MSUD is later than in the classic form, typically
between 6 months and 7 years of age.
-
3.
Intermittent MSUD. In the intermittent form, growth and intellectual development are normal. Stressors
such as infections, fever, or hunger can cause brain damage, leading to episodes of
metabolic decompensation. Such episodes are potentially catastrophic and fatal.
-
4.
Thiamine-Responsive MSUD. This form has shown favorable response to treatment with thiamine (Vitamin B1) along
with diet restrictions.
|
DIAGNOSTIC TESTING, PHYSICAL FINDINGS, AND
ICD-9-CM/ICD-10-CM
CODING |
Diagnostic testing: Diagnostic testing for MSUD includes blood and urine amino acid tests that measure
the levels of leucine, isoleucine, alloioleucine and valine. If MSUD is found, there
will be signs of ketosis and excess acid (acidosis). These are measured in the usual
newborn screening test.
Physical findings: Symptoms include:
ICD-9: 270.3
ICD-10: E70.1
|
PROGRESSION |
If the disease is not treated, MSUD can lead to seizures, coma, and death at any age.
In the intermittent type symptoms become apparent later in infancy or childhood and
are typically milder. Long-term sequelae may include developmental delays, learning
problems, seizures and motor difficulties. Even with dietary treatment, stressful
situations and illness can still cause high levels of certain amino acids. Death may
occur during these episodes.
|
TREATMENT |
When the condition is diagnosed and during episodes, treatment involves eating a protein-free
diet and correction of the metabolic consequences of the elevated amino acid levels.
A special intravenous solution decreases the leucine level (the most toxic) and corrects
the energy deficits. In the intermittent form a special diet containing low levels
of the offending amino acids is required. Even with treatment affected individuals
remain at risk for developing episodes of acute illness (metabolic crisis), often
triggered by infection, injury, failure to eat (fasting), or psychological stress.
During these episodes there is a rapid, sudden spike in amino acid levels necessitating
immediate medical intervention. For acute toxic episodes the management is the same
as in the classic form. In the Thiamine-responsive form, administration of thiamine
and consumption of a low protein diet results in a reduction of amino acid levels
to normal. Withdrawal of thiamine treatment results in a rapid rebound in the elevation
of plasma amino acid concentration.
|
SUGGESTED PROGRAMMATIC ASSESSMENT*
|
Suggested MER for Evaluation:
-
•
Clinical examination with a description of findings;
-
•
Plasma amino acid test, and urine amino acid test; and
-
•
Lab reports documenting signs of increased leucine, isoleucine, allioleucine and valine.
There may also be ketosis and acidosis.
|
Suggested Listings for
Evaluation: |
DETERMINATION
|
LISTING
|
REMARKS
|
Meets |
111.17 |
|
112.02
|
|
Equals |
|
|
* Adjudicators may, at their discretion, use the Medical Evidence of Record or the
listings suggested to evaluate the claim. However, the decision to allow or deny the
claim rests with the adjudicator.
|