The goal of this study is to better characterize the metabolic alterations and sugar structure alterations (glycosylation abnormalities) in patients diagnosed with Congenital Disorders of Glycosylation. The investigators aim to assess the safety and tolerability of oral galactose treatment in a small pilot group of Congenital Disorders of Glycosylation patients. The investigators will also determine the relationship between simple milk sugar intake (galactose dose) in the diet and the blood and urine markers of protein glycosylation abnormalities.