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To Breastfeed or Not:
PKU, Galactosemia, Other Rare Disorders
and Possible Misdiagnosis

Chris Hafner-Eaton
Corvallis, Oregon, USA
From: LEAVEN, Vol. 34 No. 4, August-September 1998, pp. 78-79

We provide articles from our publications from previous years for reference for our Leaders and members. Readers are cautioned to remember that research and medical information change over time.

A Leader receives a call from a mother whose doctor has told her she must stop breastfeeding because her child has a rare disorder. The mother has never heard of the disease and is heartbroken to learn that she must stop nursing. Medical details often become buried in emotions. This article addresses some of the issues surrounding a mother's decision to breastfeed and how a Leader can present information to her without giving medical advice.

A Leader needs to take extra care to record details about pregnancy, complications of pregnancy/labor, medications (baby and mother), birth weight, number of feedings in 24 hours, any supplements given, number of wet/soiled diapers, weight lost/gained, preliminary diagnosis, etc. The Medical Questionnaire Form (No. 91 from LLLI) can guide a Leader in taking such a history.

Two particularly rare metabolic disorders, phenylketonuria (PKU) and galactosemia, result in more than their proportionate share of crisis breastfeeding calls because physicians frequently recommend immediate weaning. Other conditions include: congenital hypothyroidism, celiac disease, cystic fibrosis, hypoglycemia, true lactose intolerance and cow's milk protein allergy. Incorrect diagnosis is another possibility.

Internationally, many ministries of health mandate that specific genetic screening tests be performed while a woman is pregnant and/or after her baby is born. In nations with planned national health schemes or public insurance programs, tests are defended because there is great public interest in early detection. While the US has no national policy on neonatal screening, all states individually require that infants be screened for at least PKU and hypothyroidism. Individual states may require other tests or procedures.

Phenylketonuria (PKU)

PKU testing, although common, is not without controversy. The test is targeted at identifying infants who, because of a liver enzyme deficiency, cannot metabolize phenylalanine, one of 20 essential amino acids. Without this early identification, PKU infants usually fail to develop normal neural pathways in the central nervous system and brain. The validity of performing mandatory PKU tests 48 hours after birth has been questioned because of the high false negative rate. A second test is usually performed at a two-week checkup. In babies testing positive for PKU, at least one more test should be performed to confirm results.

According to Riordan and Auerbach, "Breastfeeding an infant with PKU is not contraindicated as was previously believed. Human milk has relatively low levels of phenylalanine" when compared with cow's milk formulas. Miller and Chopra and others recommend that total or partial breastfeeding should be encouraged in the PKU infant. In addition, these infants should have their phenylalanine blood levels monitored regularly. Leaders might forewarn mothers to watch for symptoms of thrush and/or sore nipples because PKU infants are more prone to yeast growth.


Galactosemia is also a metabolic enzyme deficiency/absence condition which is transmitted through a recessive genetic trait. Riordan and Auerbach state the incidence of galactosemia as one in every 85,000 births or about 47 infants per year in the US. Infants lacking a critical liver enzyme (responsible for converting galactose to glucose) risk severe mental retardation and liver damage. The symptoms of galactosemia are vague, especially since the newborn appears normal.

However, soon after birth mothers report that their infants have profuse vomiting, poor weight gain, wasting and lethargy. This usually prompts them to seek medical attention and testing (or perhaps phone La Leche League first). As stated in the BREASTFEEDING ANSWER BOOK, page 308, this enzyme is heat-sensitive and results may be skewed if the sample sits in a hot mailbox. Failing to identify galactosemia may have dire results while false-positive test results can lead to unnecessary weaning. Practitioners often err on the side of weaning when there is doubt. Thus, mothers should be encouraged to request an immediate retest with special handling. Such testing may be difficult in areas where there is no reliable way of protecting the sample from heat. There is no intermediate or partial breastfeeding option for these infants. They must be totally weaned promptly and fed a galactose-free formula such as Nutramigen. A bottle or cup must be used; use of a supplemental nursing system is not possible because it could allow ingestion of human milk. Note that this is a very different situation than PKU, so a clear diagnosis is critical.

Infant Diarrhea

A third possibility where practitioners recommend weaning originates from a possible misdiagnosis. Infant diarrhea may result in more misdiagnoses than any other cause. Both parents and practitioners need to recognize that a breastfed baby's stool is normally looser and possibly more frequent than a formula-fed baby's stool. If true diarrhea is determined, a Leader can ask the mother what diagnosis was provided and why weaning is thought to be necessary. Worldwide, diarrhea is the leading cause of infant death, so Leaders need to take this seriously. In some areas of the world, including parts of the US, physicians have been taught that diarrhea is an indication for temporary weaning and the feeding of oral rehydration therapy or electrolyte solution. Studies support the fact that breastfeeding should continue. Human milk, unlike formula and other milk products that are best avoided while the baby has diarrhea, is a natural fluid that is easily and rapidly digested (Ewer 1994).

If the baby is dehydrated enough to need rehydration, the practitioner may need to give fluids intravenously. Even under these circumstances, breastfeeding may continue. Often, diarrhea is self-limiting, but if it has continued for more than a week or the baby is under one month old, something other than a passing virus may be the cause.

Mothers are sometimes informed by well-meaning practitioners that their babies are "allergic" to their milk. It is important to find out exactly what was said and under what circumstances. Did the practitioner recommend a trial of temporary weaning or suggest that the mother alter her diet for at least two weeks? If the baby has been diagnosed as lactose intolerant but has been doing fine on breast milk, more information will be needed. Primary lactose intolerance or primary lactase deficiency, where baby is lacking lactase from birth, is exceptionally rare but immediately apparent by profuse diarrhea and vomiting from the time the mother's milk comes in. In this case, a special lactose-free formula must be given. Lactose intolerance that does not originate from the time the mother's milk came in is common in certain populations. It is caused by a gradual decrease in the body's production of lactase. It cannot be the cause of diarrhea in a child younger than three to five years of age.

If a baby had been thriving and a lactose intolerance diagnosis is given, the Leader may ask some questions to determine whether mother or baby has recently had antibiotic therapy (possible yeast overgrowth or thrush), a change in diet (possible allergy to something in mother's/baby's diet or excess consumption of fruit juice by baby) or a change in nursing pattern (possible foremilk/hindmilk imbalance or even oversupply). Obtaining details about stool color, viscosity, odor and frequency helps provide clues to the true underlying cause of the diarrhea. Weaning due to misdiagnosis of lactose intolerance can be minimized by providing mothers with solid research references to share with their practitioners. Of course, we may also remind parents that they have the right to seek a second opinion.

Leaders Providing Support

Clearly, these situations present challenges for Leaders. Discussing the mother's feelings both before and after completing the Medical Questionnaire Form is vital. Once pertinent information has been gathered and the Leader has helped a mother identify her feelings. ask her if she would like some resource information. A Leader can provide the references in this article or the BREASTFEEDING ANSWER BOOK for the mother and her practitioner. She can also contact the Area Professional Liaison (APL) Leader for the most up-to-date information. The PL Leader can access the LLLI Center for Breastfeeding Information. A Leader may suggest retesting and/or a second opinion to the mother; however, she may not directly question the diagnosis. Listening carefully and asking the mother what she thinks and wants can very helpful.

Remember, a rare medical diagnosis puts stress on a mother and her family, so be clear, supportive and patient. A follow-up call is a good idea. A mother who has been told to wean or told that her baby has some illness may have concerns that continue after the crisis moment is over.


Amir, L., Hoover, K., Mulford, C. Candidiasis and Breastfeeding. LLLI Lactation Consultant Series, New Jersey: Avery, 1995; 7.

Brown, K. Dietary management of acute childhood diarrhea: optimal timing of feeding and appropriate use of milks and mixed diets. Pediatrics 1991; 118 (4); S92-S98.

Brown, K., Lake, A. Appropriate use of human and nonhuman milk for the dietary management of children with diarrhoea. J Diarrhoeal Dis Res 1991; 9(3):168-85.

Ewer, et. al. Gastric emptying in preterm infants. Arc Dis Child 1994; 71:F24-F27.

Grad, F. The Public Health Law Manual, 2nd ed. Washington, DC: American Public Health Assoc, 1990; 9-25.

Lawrence, R. Breastfeeding: A Guide for the Medical Profession, 4th ed. St. Louis: Mosby, 1995; 348.

McCabe, L. et al. The management of breastfeeding among infants with phenylketonuria. J Inher Metab Dis 1989;12:467-74.

Miller, S., Chopra, J. Problems with human milk and formulas. Pediatrics 1984; 74:639-47.

Mohrbacher, N., Stock, J. BREASTFEEDING ANSWER BOOK. Schaumburg, Illinois: LLLI. 1997; 280-83, 308-9, 312-13.

Riordan, J., Auerbach, K. Breastfeeding and Human Lactation. Boston: Jones and Bartlett, 1993; 498-500.

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