Infantile galactosemia can be caused by inborn errors of galactose metabolism or other rare causes like Fanconi-Bickel syndrome, congenital porto-systemic shunting and multiple hepatic arterio-venous malformations. All these disease entities are however not commonly seen. We report a case of transient infantile galactosemia who first presented in the 1990s, for which no underlying pathology could be identified despite extensive investigations. The diagnosis had not been apparent until after more than a decade, at that time the patient was lost to contact. Considering the potential diagnosis an important and significant one, efforts were made by the case pathologists and clinicians to search for the patient. Ethical dilemmas were encountered during the search of the patient, which involved issues of patient confidentiality and autonomy, and the doctors' duty-to-care. Modern biochemical and molecular testing confirmed the diagnosis after the patient was finally found. The case illustrates the power of molecular testing to retrospectively diagnose an inherited metabolic disease when biochemical abnormalities have subsided, the value of an accurate and precise diagnosis, and the importance of appropriate genetic counselling in an apparently asymptomatic patient in the era of personalized medicine.