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 firstname.lastname@example.org.
References: uptodate.com, emedicine.medscape.com.