To Anne N-K,RPh: A very interesting situation.  I researched what I could but
there is so little available & nothing re: bf that I could find.  I have only
had 1 case in 12 yrs as a WIC RD and that babe was treated w/ MSUD Powder.
 I'll give you my thoughts.
MSUD is a decarboxylation defect affecting the branch chain AA leucine,
isoleucine & valine (partic. leucine).  Since I don't know of any tx other
than avoidance of these AA, if this were my client I would be very cautious.
 Comparison of BM vs ABM shows lower levels of all 3 AA in BM, and it is
possible, as we are finding now, that other special *critters* reside in BM
which inhibit or slow abnormal metabolic problems, but again, I have not seen
any research.  The latest edition of "Nutrition & Diet Tx" (Krause &
Mahan--most RDs have a copy in their possession) says that once returned to
nl blood levels, esp. leucine, small amts of ABM or cow's milk may be
supplemented to provide the BCAA, so, I would think, techically, once
stabilized, larger amts of BM could be supplemented because of the lowered AA
levels.  However VERY CAREFUL BLOOD MONITORING WOULD HAVE TO BE DONE SO THAT
THE AA LEVELS DID NOT AGAIN BECOME TOXIC.  N&DT recommended maintaining
leucine levels betw. 2 & 5 mg./dl. Levels > 10 mg/dl can lead to
alpha-ketoacidemia & neuro symptoms.  So...if I were having this problem I
would probably put the infant on MSUD Powder (M..J..) until the leucine
levels were wnl but have the mom pump to keep her milk going (Note: MSUD
powder  has no leucine,isoleucine or valine.)  I would also teach the mom to
feed w/ the infant as close to her breast as possible, definetly skin to skin
(to reduce the trauma of having to wean) & perhaps feed by cup.  I would not
recommend SNS because of the temptation to the baby of take the nipple in his
mouth, and I would try to keep artificial nipples away if possible.  I would
also recommend she use her finger as a pacifier to continue that mouth/skin
attachment.  It may be that the levels would drop quickly and she could
resume short nursings soon?

Specifically, to respond to your ??, in my VERY humble opinion, I think that
the delay of symptoms would be insignificant but that yes, once controlled,
BF could be resumed under very careful circumstances.  This is such a
wretched disease; I think worse that PKU.  Please keep me informed on the
progress of this baby, and on any new research you may find.  Hope I could be
of some help.  Sue,RD