Classical galactosemia Elucidating the spectrum of clinical outcome

Classical Galactosemia is an inborn error of metabolism, a disease in which galactose (milk sugar) is not processed correctly in the cells of the body. The enzyme galactose-1-phosphate uridylyltransferase (GALT) is an enzyme essential for one of the steps in the conversion of galactose into glucose, which is used by the body for energy. Galactosemia literally means galactose in the blood. In patients with Classical Galactosemia (CG), the enzyme GALT is not working properly as a result of inherited changes in the DNA. The accumulation of galactose in the blood leads to toxic products upstream of the GALT enzyme and a shortage of products downstream of the GALT enzyme. Both mechanism are presumed to contribute to the complications observed in patients such as motor developmental delay, speech developmental delay, a below average IQ, cognitive impairment, movement disorders, and in most female patients premature ovarian insufficiency (POI). The clinical outcome of patients is highly variable and ranges from severely affected to completely normal, which is poorly understood.
The aim of this thesis is to elucidate the broad spectrum of clinical outcome of CG and to search for (prognostic) markers of clinical outcome. Part 1 of this thesis explores the clinical and biochemical outcome of patients and in Part 2 potential (bio)markers and their association with clinical outcome are investigated. To improve knowledge on disease and treatment we developed patient education materials for children and adolescents with inborn errors of metabolism and tested these materials in Part 3.