title: False-Positive Newborn Screen Using the Beutler Spot Assay for Galactosemia in Glucose-6-Phosphate Dehydrogenase Deficiency.
abstract: Classical galactosemia is detected through newborn screening by measuring galactose-1-phosphate uridylyltransferase (GALT) in the USA primarily via the Beutler spot assay. We report on an 18-month-old patient with glucose-6-phosphate dehydrogenase (G6PD) deficiency that was originally diagnosed with classical galactosemia. The patient presented with elevated liver function enzymes and bilirubinemia and was immediately treated with soy-based formula. Confirmatory tests revealed deficiency of the GALT enzyme, however, full-sequencing of GALT was normal, suggestive of a different ideology. The Beutler spot assay uses three other enzymatic steps in addition to GALT. A deficiency in either of these enzymes can result in suspected decreased GALT activity when using the Beutler assay. Congenital Disorders of Glycosylation screening for phosphoglucomutase-1 deficiency was negative. Quantitative analysis of G6PD enzyme in red blood cells showed a severe deficiency and a deletion in G6PD. Soy-formula, the standard treatment for galactosemia, has been reported to trigger hemolysis in G6PD deficient patients. G6PD and phosphoglucomutase-1 deficiencies should be considered when confirmatory tests are negative for pathogenic variants in GALT and galactose-1-phosphate level is normal.
authors.affiliation: Hayward Genetics Center, Tulane University School of Medicine, 1430 Tulane Ave., Mailbox #8631, New Orleans, LA, 70112, USA. gstuhrma@tulane.edu.
authors.forename: Grace
authors.initials: G
authors.lastname: Stuhrman
authors.affiliation: Hayward Genetics Center, Tulane University School of Medicine, 1430 Tulane Ave., Mailbox #8631, New Orleans, LA, 70112, USA.
authors.forename: Stefanie J
authors.initials: SJ
authors.lastname: Perez Juanazo
authors.affiliation: Hayward Genetics Center, Tulane University School of Medicine, 1430 Tulane Ave., Mailbox #8631, New Orleans, LA, 70112, USA.
authors.forename: Kea
authors.initials: K
authors.lastname: Crivelly
authors.affiliation: Hayward Genetics Center, Tulane University School of Medicine, 1430 Tulane Ave., Mailbox #8631, New Orleans, LA, 70112, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Smith
authors.affiliation: Hayward Genetics Center, Tulane University School of Medicine, 1430 Tulane Ave., Mailbox #8631, New Orleans, LA, 70112, USA.
authors.forename: Hans
authors.initials: H
authors.lastname: Andersson
authors.affiliation: Hayward Genetics Center, Tulane University School of Medicine, 1430 Tulane Ave., Mailbox #8631, New Orleans, LA, 70112, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Morava