Dr. Greene, I am 8 months pregnant with a child affected by Propionic Acidemia, an inborn error of metabolism. My Doctor and Dietician warn that I will not be able to breastfeed, as the milk cannot be accurately measured. I will be able to pump, but the bonding attached to breastfeeding is something I really wanted. Do you know of any successful stories of breastfeeding with metabolic patients?

Each meal is a matter of life and death for children with propionic acidemia. Children need protein in order to grow and thrive, but for these children extra protein is a deadly poison.

Here's the problem: The amount they need to grow is a little more than the amount they can handle. Each meal becomes a delicate balancing act that can make the difference between normal development and long-term disability.

Knowing that your baby has this precarious illness must make the desire to nurse and comfort your baby even stronger. But, as cruel as it seems, even breastmilk can be dangerous, unless it is used in just the right way.

Propionic acidemia is one of what we call the inborn errors of metabolism. The individual metabolic disorders are rare, but taken as a group they are fairly common. I do know women who have nursed successfully with metabolic disorders. Some of the metabolic disorders make nursing difficult but still a great benefit.¹ Others make nursing harmful.²

Normally, when we eat protein in our food, our enzymes break the protein down into molecular building blocks. We then reassemble these into the specific protein molecules and other substances our bodies need. Proteins are made up of amino acids.

In propionic acidemia, one little enzyme is missing, but this is enough to change an entire life. Without the enzyme propionyl CoA carboxylase, some common amino acids in protein (isoleucine, valine, threonine, and methionine), are only partially processed. One of the intermediate stages, propionic acid, builds up in the bloodstream.

The propionic acid causes poor feeding, vomiting, dehydration, floppiness, and lethargy, which usually show up in the first weeks of life, and can progress rapidly to coma and death. Seizures occur in about 1/3 of babies. If a baby survives the first attack, similar episodes may occur during an unrelated infection, constipation, or following a high-protein meal.

Some children sail through the early months without apparent problem and don't come to attention until much later in life.

Before it was recognized and treated, propionic acidemia was usually fatal. With right treatment, it is possible for children to grow and develop normally. The right treatment is crucial. It greatly improves children's odds but is not the whole story.

Some children are treated perfectly and still have bad outcomes. Others receive no treatment at all and thrive. Even within the same family, there can be wide variability of this disease. One boy was first diagnosed at age 5 because of mental retardation; his 13-year-old sister turned out to have the same level of enzyme deficiency but had no symptoms at all!³

The cornerstone of treatment is to restrict protein. Other measures can be helpful (supplementing with L-carnitine, supplementing with thiamine,⁴ using antibiotics to kill gut bacteria that produce amino acids, using alkaline treatment to decrease acid, treating any constipation immediately, etc), but without restricting protein, none of the other treatments help.

Generally with the low-protein diet, regular protein must be restricted to 1.0-1.5 g/kg per 24 hours.