Tina -

MSUD is an autosomal recessive disorder of the metabolism of
branched chain amino acids (leucine, isoleucine and valine).  An
enzyme is missing that is needed for breaking down the amino acids.
They accumulate and the result is mental retardation.

Babies with this disorder are normal at birth, but after eating milk with
protein they develop apnea and convulsions, progressive neurologic
dysfunction, a shrill cry and a peculiar maple syrup-like odor.  They
alternate between periods of hyperactivity and flaccidity and may have
seizures.  Poor suck and irregular respiration is common.  Babies may
die in the first few weeks or months.  In untreated survivors brain
damage and mental retardation is common.  The incidence is 1/216,00
live births.

 The limit for leucine (which accumulates  to the greatest extent) is
40-100 mg/kg/day for 0-6months and 40-75 mg/kg/day for 6-12 months.
 Colostrum contains 221 mg / 100 ml and mature breast milk contains
110 mg/ 100 ml.

So, as with PKU, some breast milk is allowed but the amount needs to
be limited so the baby won't get too much protein.  Babies are fed a
special powder that does not have the offending amino acids in it.  Our
metabolic dietitian said that limited breastfeeding should be permitted,
but of course the MD always has the final say.

Rachelle Lessen, RD, IBCLC
Philadelphia, PA        mailto:[log in to unmask]