Galactitol, Quantitative, Urine
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Galactosemia is an autosomal recessive disorder that results from a deficiency of 1 of the 3 enzymes catalyzing the conversion of galactose to glucose: galactose-1-phosphate uridyltransferase (GALT), galactokinase (GALK), and uridine diphosphate galactose-4-epimerase (GALE). GALT deficiency is the most common cause of galactosemia and is often referred to as classic galactosemia. The complete or near complete deficiency of the GALT enzyme is life threatening. If left untreated, complications include liver failure, sepsis, cognitive and intellectual disabilities, and death. Galactosemia is treated with a galactose-free diet, which allows for rapid recovery from the acute symptoms and a generally good prognosis. Despite adequate treatment from an early age, children with galactosemia remain at increased risk for developmental delays, speech problems, abnormalities of motor function, and females are at increased risk for premature ovarian failure. Based upon reports by newborn screening programs, the frequency of classic galactosemia in the United States is approximately 1 in 30,000.
Galactose levels may be continuously elevated in individuals affected with galactosemia even with a galactose-restricted diet regimen due to an endogenous production of galactose. The reduction of galactose to galactitol is an alternate pathway of galactose disposition when galactose metabolism is impaired. The excretion of abnormal quantities of galactitol in the urine of patients is characteristic of this disorder, and patients may have abnormal levels of galactitol even with dietary compliance. Daily consumption of galactose may cause urine levels to rise thus providing information on effectiveness of or compliance with treatment, but unlike erythrocyte galactose-1-phosphate (GAL1P) and plasma galactose, urine galactitol levels usually do not provide insight into acute and transient effects of galactose intake.
Monitoring effectiveness of treatment in patients with galactosemia
Establishing a baseline level prior to initiating treatment for galactosemia
The concentration of galactitol is provided along with reference ranges for patients with galactosemia and normal controls.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-11 months: <109 mmol/mol creatinine
1-3 years: <52 mmol/mol creatinine
4–17 years: <16 mmol/mol creatinine
> or =18 years: <13 mmol/mol creatinine
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Online Mendelian Inheritance in Man. 230400, 230200, and 230350, respectively. National Center for Biotechnology Information. Available at www.ncbi.nlm.nih.gov/Omim
2. Berry GT: Classic Galactosemia and Clinical Variant Galactosemia. In GeneReviews, Edited by RA Pagon, MP Adam, HH Ardinger, et al. University of Washington, Seattle; 1993-2015. 2000 Feb 4 (Updated 2014 Apr 3). Available at: http://www.ncbi.nlm.nih.gov/books/NBK1518/
3. Holton JB, Walter JH, Tyfield LA: Galactosemia. In The Metabolic and Molecular Basis of Inherited Disease. Vol 1. Eighth edition. Edited by CR Scriver, AL Beadut. New York, McGraw-Hill Book Company, 2001, pp 1553-1587