

Answer to Medical Mystery Monday #38


The answer to yesterday’s mystery is … galactosemia! Great job O’B1 and James K. for diagnosing the patient.

Galactosemia is a genetic disease in which the patient lacks an enzyme (called GALT) that breaks down a sugar called galactose. Lactose, the sugar in breast milk, is composed of galactose and glucose. Because the breast milk cannot be broken down, galactose builds up inside the baby’s tissues and causes all of the symptoms of galactosemia.

A lot of the galactose consumed in breast milk is metabolized in the liver. For that reason, its buildup causes signs of liver dysfunction such as jaundice (yellow skin) and enlarged liver. The baby is vomiting and not growing properly because of its intolerance of its only source of food. Galactose can be deposited in the eye as well, forming the cataracts shown in the picture.

Newborns are routinely screened for galactosemia at birth in the US, which is why I described our patient hailing from a different country. The patient would be tested for GALT enzyme activity to confirm the diagnosis. Patients with this disease are treated by eliminating dairy products from the diet, such as giving the infant a soy-based formula. Occasionally, patients with galactosemia may have long-term complications even after eliminating dairy, such as developmental delay or slow growth.

Thanks again to the reader who suggested featuring this fascinating disease. If you have an idea for a future medical mystery, you can email me at


Marianne DiNapoli

4 Responses

  1. ProudParent says:

    Thank you Marianne for showcasing this disease!

    My son was diagnosed with galactosemia when he was five days old, and we along with his doctors are learning new things about it daily. An interesting fact about it is how different it is with the different sexes. Sadly, females face much greater complications usually including infertility and going through menopause around the age of 14.

    Thanks again!

  2. ColorMaven says:

    Hi. Not arguing here but want to learn… Given the information that was provided, what clue provided the diagnostic distinction for galactosemia vs. congenital rubella?

  3. Christy says:

    Thanks very much for highlighting galactosemia! I live in NC and just happened to do a Google News search on galactosemia today… very cool to have your piece come up. We have a 7.5 year old boy with classic galactosemia. He was diagnosed at 7 days old through newborn screening. So far he is doing well, but explaining why he has such a strict diet can be a challenge. We always appreciate media covereage of this very rare condition so that more people have at least heard of it!

  4. Proud Parent – that is truly fascinating. Thanks for the info.

    ColorMaven – As people were posting answers, I realized that the case I presented was EXTREMELY similar to how congenital rubella would present. Thanks for pointing that out. I meant to write that in the body of the post but it slipped my mind. The only distinguishing details between the two presentations are:
    -Rubella commonly presents with cardiac defects (PDA, pulmonic stenosis) and hearing loss, which were not mentioned in the case.
    -Galactosemia commonly presents with vomiting, but rubella does not.

    Christy – You are very welcome! Hope you and your son are well.