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MSUD is an inborn error of branched chain amino acids (BCAA) metabolism in which the a-ketoacids derived from BCAA (leucine, isoleucine and valine) cannot be fully catabolized to their respective short-chain fatty acids because there is a deficiency of the branched chain ketoacid dehydrogenase complex (BCKD) (see diagram below). One or more of the branched chain a-ketoacids (BCKA) that accumulate (a-ketoisocaproic acid, a-keto-þ-methylvaleric acid, and a-ketoisovaleric acid) is (are) toxic. The major initial feature is encephalopathy and there may be a ìmaple syrupî or ìburnt sugarî odor detectable in the cerumen in the ear or urine.
History and examination
If the infant has any sign of illness or a markedly elevated leucine level, he/she must be seen by a metabolic physician the same day of notification from the newborn screening program. UNDER ANY CIRCUMSTANCE, A METABOLIC PHYSICIAN MUST BE CONSULTED.
History
The neonate may have a normal history. The first symptoms include refusal to feed, lethargy and change in mental status.
Examination
The infant may appear well. When symptomatic, the neonate with MSUD typically has the clinical picture of early encephalopathy and brain edema. Signs as subtle as poor Moro reflex are very concerning. The absence of maple syrup odor should not deter consideration of the diagnosis.
ANY signs of illness must be treated as a medical emergency and treated immediately. See Acute Illness Protocol, MSUD
If the child appears well it is still essential
to refer to the metabolic center to ensure that the child and
family receive the necessary treatment and guidance to prevent
morbidity.
Contact the metabolic physician for
markedly elevated leucine 
Discussion with parents for
elevated leucine
ENSURE THAT THE REPEAT NEWBORN SCREENING SAMPLE IS SENT TO THE
STATE LABORATORY AND THE RESULT OBTAINED ASAP
(Go to NNSGRC
for the state labs) |
