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Verbal dyspraxia and galactosemia
Amy Leigh Webb1, Rani H Singh, Mary Jane Kennedy
1Emory University Graduate School of Arts and Sciences, Department of Biological and Biomedical Sciences, Division of Nutrition and Health Sciences, Atlanta, Georgia 30322, USA.
Pediatric Research
|February 22, 2003
Summary
A novel breath test accurately measures galactose metabolism in patients with galactosemia, reflecting their genetic makeup. This test also effectively predicts verbal dyspraxia, a common complication, by identifying specific biochemical risk indicators.
Area of Science:
- Biochemistry
- Genetics
- Metabolic Disorders
- Speech Pathology
Background:
- Classical galactosemia is an inherited metabolic disorder caused by deficient galactose-1-phosphate uridyltransferase (GALT) enzyme activity.
- Verbal dyspraxia is an unusual but significant neurodevelopmental outcome observed in individuals with galactosemia.
- Accurate assessment of galactose metabolism and identification of risk factors for verbal dyspraxia are crucial for patient management.
Purpose of the Study:
- To validate a simplified breath test measuring total body galactose oxidation against patient genotype.
- To evaluate biochemical indicators for predicting verbal dyspraxia in galactosemia patients.
- To assess the relationship between galactose metabolism, genotype, and the incidence of verbal dyspraxia.
Main Methods:
- A (13)C-galactose bolus was administered to 13 controls and 42 galactosemia patients.
- Cumulative percentage dose (CUMPCD) of (13)CO(2) in expired air was measured to assess galactose oxidation.
- Speech evaluations were conducted, and biochemical markers (erythrocyte galactose-1-phosphate, urinary galactitol, GALT activity) were analyzed.
Main Results:
- Breath test CUMPCD values correlated with GALT genotype, distinguishing severely vs. mildly impaired enzyme activity.
- Patients with verbal dyspraxia exhibited significantly lower CUMPCD values and higher erythrocyte galactose-1-phosphate and urinary galactitol levels.
- Specific thresholds for CUMPCD (<5%), erythrocyte galactose-1-phosphate (>2.7 mg/dL), and urinary galactitol (>135 mmol/mol creatinine) were associated with increased odds of dyspraxia.
Conclusions:
- The (13)C-galactose breath test effectively reflects total body galactose oxidation and correlates with genotype in galactosemia.
- This breath test serves as a sensitive predictor for verbal dyspraxia in galactosemia patients.
- Biochemical markers like erythrocyte galactose-1-phosphate and urinary galactitol are valuable indicators of dyspraxia risk.