Galactosemia is an autosomal recessive disease, caused by the deficit of any of the four enzymes involved in the metabolism of galactose, derived from the disaccharide lactose, on its way to becoming glucose. Knowledge of this pathology and a high index of suspicion will allow early diagnosis and treatment, thus decreasing the associated complications and even mortality. We will present a brief summary of the disease in the context of a patient treated in our neonatology service.