Sorry this reply is so late, I have been busy all week trying to catch up after the fabulous ILCA conference in Acapulco. Methylmalonic aciduria is a symptom of an inherited metabolic defect. There are several defects that cause this symptom. In infants with high methylmalonic acid due to a defective transferase, administration of high doses of cobalamin (vitamin B-12) by injection or iv will reduce the methylmalonic acid levels. The other half of infants with methylmalonic aciduria have defective methylmalonic coenzyme A mutase, which is sometimes treated by special formulas without the amino acids isoleucine, threonine, valine, methionine; which use this pathway for metabolism. The infant is usually given some regular formula so they get some of these amino acids. Of course, breast milk has less of these amino acids than formula, but it can be difficult to find a physician who will work with a breastfeeding mother. I had an infant in my practice with a cobalamin C deficiency (one of the enzymes that changes dietary B12 to it's active form), and the physicians insisted that the mother wean, because "we don't know what the protein content of your milk is". Mom was grieving her ill infant, and did not have the energy to argue that they would just test the baby's blood the way they would to find the right balance of each formula to get the right balance of breastmilk and the special formula. This baby had both methylmalonic aciduria, and homocysteinuria. Any metabolic acidosis can be lethal, so it is important that this baby be treated. But if he or she is just missing the transferase, there is no need to wean from the breast at all. -- Catherine Watson Genna, IBCLC New York City mailto:[log in to unmask] *********************************************** The LACTNET mailing list is powered by L-Soft's renowned LISTSERV(R) list management software together with L-Soft's LSMTP(TM) mailer for lightning fast mail delivery. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html