Classic galactosemia in the differential diagnosis of neonatal low gammaglutamyltransferase cholestasis

Neonatal cholestasis is a diagnostic challenge that warrants extensive investigation as there can be serious sequalae such as liver failure, cirrhosis, or other extrahepatic complications. To differentiate the etiology of cholestasis, a distinction can be made between high and low gamma-glutamyltransferase (GGT) cholestasis. Low GGT cholestasis points towards progressive familial intrahepatic cholestasis type 1-2 and 4-6, bile acid synthesis disorders, tight-junction protein type 2 deficiency and some forms of hypopituitarism. Classic galactosemia is generally not included in the differential diagnosis of low GGT cholestasis. Here, we demonstrate low GGT cholestasis in 9 consecutive patients with classic galactosemia at the University Hospitals of Leuven, Belgium. All neonatal cholestasis should be managed with prompt cessation of galactose intake, but in classic galactosemia it can be lifesaving. We now add that low GGT cholestasis increases the likelihood of galactosemia. Conversely, high GGT cholestasis could point to other causes, like biliary atresia, where there may be no need to stop breastfeeding. In galactosemia, we observe a rise in GGT after initiation of a galactose-free diet, which we suggest may be partially explained by the normalization of bile acid transporter glycosylation.