Advances and Challenges in Classical Galactosemia. Pathophysiology and Treatment

Abstract Classical galactosemia is caused by the genetic deficiency of galactose-1-phosphate-urydyl-transferase resulting in clinical symptoms development during the first weeks of life including jaundice, hypotonia, lethargy, emesis, hepatomegaly, among others. Currently, dietary restriction of galactose is considered the standard for classical galactosemia management. For several years, severe dietary galactose restriction was considered necessary, implying restriction not only of dairy products, but also fruits, vegetables, legumes, and viscera. Such management failed to improve or prevent the appearance of long-term complications, by contrast, such restrictive approach may lead to nutritional deficiencies development. Thus, the last consensus suggests guidelines that are more flexible. In addition, the lack of knowledge regarding the physiopathology of the disease, and the toxicity threshold of the metabolites accumulated, make even more difficult to propose novel and more effective therapeutic approaches. This review summarizes the current state of knowledge regarding classical galactosemia in terms of physiopathology, long-term complications, newborn screening and genetic variants and their implications on galactosemia treatment, summed to the challenges that researchers working on this disease must address in future studies including the analysis of galactose content in foods, galactose tolerance threshold and search for novel therapeutic targets.

Identification and analysis of galactose-1-phosphate uridyltransferase gene mutations in children with galactosemia / 中华实用儿科临床杂志

Objective To investigate the mutation of galactose-1-phosphate uridyltransferase gene (GALT gene) of galactosemia children by molecular methods.Methods Two children with galactosemia were investigated.The peripheral blood mononuclear cells were separated and total RNA was extracted.Then,whole cDNAs of GALT were amplified by reverse-transcription polymerase chain reaction;The PCR products were subcloned into T-easy vector and the positive clones were selected and sequenced;meanwhile,the PCR products were also digested by restricted enzymes and identified by restriction fragment length polymorphism.Results Two novel mutations were found in 2 children.In one child,A was changed into G in nucleotide 1006 of GALT gene,which led to amino acid residue M336V mutation.In the other child,A in nucleotide 779 of GALT gene was changed into T and led to amino acid residue H260L mutation.The 2 mutations were both missense mutation and heterozygous mutation.Conclusions Gene diagnosis is an useful method to improve the accuracy of galactosemia diagnosis and will provide valuable references for prenatal diagnosis,hematopoietic stem cell transplantation and gene therapy.

Association of fungal sepsis and galactosemia.

Galactosemia is one of the rare inborn errors of metabolism, which if detected early can be treated effectively. Galactosemic infants have a significant increased risk of developing sepsis. E. coli sepsis is a known entity, and also an important cause of early mortality in these children. But fungal sepsis in these patients is rarely reported. Here is a case of 45 day-old child who presented with fungal sepsis, which on investigation turned out to be galactosemia.

A Case of Classical Galactosemia caused by Compound Heterozygous Mutations of the GALT Gene

Classical galactosemia is an autosomal recessive disorder of galactose metabolism, caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). Buildup of galactose-1-phosphate is toxic at high levels and can damage the liver, brain, eyes, and other vital organs. The case presented here was that of an 11-day-old female infant who had elevated galatose levels upon initial neonatal screening test with persistent cholestatic jaundice, coagulopathy, and hepatomegaly. The patient was transferred due to aggravation of clinical symptoms including bleeding and jaundice. She had a delayed galactose free diet because of an inappropriate diagnosis. We quickly provided her with a lactose/ galactose-restricted diet as per her final diagnosis. Clinical and laboratory results were improved after a few days of treatment. For confirmatory testing for classical galactosaemia, we simultaneously analyzed for GALT enzyme activity and allele-specific PCR/fragments for seven mutations and two polymorphisms in the GALT gene. We were able to find several GALT-deficient and compound heterozygous mutations of the GALT gene.

Galactosemia / 한양의대학술지

Galactosemia, a term that denotes the presence of galactose in the blood, is the name of rare inborn error of galactose metabolism due to a deficiency of the enzyme galactokinase (GALK), galactose-1-phosphate uridyltransferase (GALT) and uridine diphosphate-galactose 4-epimerase (GALE). GALT deficiency is the most common and shows the most severe clinical manifestation, including hepatomegaly, cataracts, and mental retardation. The main symptom of GALT deficiency is juvenile cataracts. GALE deficiency has two different forms; benign and severe forms. The benign form has no clinical significance, however, the severe form shows the same clinical manifestations as those of GALT deficiency.

An Analysis of Two-Year Experience in Neonatal Screening / 대한진단검사의학회지

BACKGROUND: This study was undertaken to evaluate whether the currently used cut-offs are appropriate and whether there is a significant relationship between false positive results and post-natal well being in neonatal screening. METHODS: During the period of January 2001 through December 2002 at Samsung Medical Cen-ter, neonatal screening tests for TSH, free thyroxine (FT4), phenylketonuria (PKU), galactosemia and 17-hydroxyprogesterone (17-OHP) were performed in newborns using commercial ELISA kits. We reviewed the recall rates at currently used cut-offs and analyzed the relationship between false positive results and postnatal well-being. RESULTS: We obtained false positive results of 2.42%, 0.86%, 1.5%, 0.95% and 0.97% for TSH, FT4, PKU, galactosemia, and 17-OHP, respectively. Twelve babies out of 5, 918 was diagnosed with hypothyroidism. The false positive results of 17-OHP and FT4 were mostly seen in premature babies. Simultaneous false positive results of 17-OHP and other neonatal screen such as FT4 or galactosemia showed poor prognostic outcome in premature babies (odds ratio 6.08, P=0.0006). CONCLUSIONS: In galactosemia, PKU, and 17-OHP, it would be reasonable to modify the cut-offs to 99.7 percentile after measuring those substances from enough number of healthy neonates. The babies who have been treated with L-thyroxine by the current cut-offs of TSH or FT4 were relatively large in number, thus, prospective follow-up of evaluation of the cut-offs of TSH or FT4 is necessary. Also, a simultaneous positivity of 17-OHP and FT4 or galactosemia could be considered as a poor prognostic factor in postnatal well-being.

Analysis of the Galactose-1-Phosphate Uridyltransferase (GALT) Gene in a Duarte Variant/classical Galactosemia (D/G) Compound Heterozygote / 대한소아소화기영양학회지

Galactosemia is a rare autosomal recessive disorder caused by the deficiency of galactose-1-phosphate uridyltransferase (GALT) enzyme activity. Classic galactosemia (G/G) is due to severe GALT deficiency in the presence of a GALT gene mutation, whereas Duarte variant (D/D) has 50% of normal GALT activity and benign clinical course. The D2 allele of Duarte variant is linked to a promoter deletion 5' to the translation start site (-119 to -116 delGTCA) in addition to N314D. So, Duarte variant/classical galactosemia (D/G) compound heterozygotes have relatively mild clinical manifestation than classical galactosemia and can be differentiated from classical galactosemia or Duarte variant by mutational analysis. We report a case of D/G galactosemia compound heterozygote proven by the reduction of GALT enzyme activity in erythrocytes and mutation analysis of GALT gene, which revealed N314D polymorphism and -119 to -116 delGTCA.

Galactosemia Detected by Neonatal Screening Test

PURPOSE: The genetic disturbance of galactosemia is expressed as a cellular deficiency of either galactose-1-phosphate uridyltransferase(GALT) or galactokinase(GALK) or UDP galactose 4-epimerase(GALE). To find-out the pattern of galactosemia in Korea, we retrospectively analyzed cases of galactosemia detected by neonatal screening program. METHODS: We analyzed medical records of patients who visited Soonchunhyang University Hospital at age of 1 month after showing abnormalities in neonatal screening of galactosemia. For accurate diagnosis, galactose was measured by enzyme immunoassay(EIA) and fluorophotometer, also galactose-1-phosphate by fluorophotometer. Enzyme activities of GALK, GALT and GALE in RBC and galactose-1-phosphate were measured by radioisotope assay(RIA). Beutler test were done. Patients went on a lactose-free diet and follow-up tests for galactose, galactose-1-phosphate level and enzyme activity were performed. RESULTS: 10 patients(male : 6, female : 4) were diagnosed as galactosemia. Two patients had GALK deficiency and two had GALT deficiency. Six were GALE deficient showing the largest number. In two patients with GALK deficiency, GALT and GALE activities were normal but GALK activities showed respectively reduced activity. For GALT deficiency, two patients had low GALT activity in RBC and showed genotype of Duarte 2/G(galactosemia) in DNA analysis. In one patient, GALT activity was normal. Three patients seemed to be heterozygote state of GALE deficiency according to GALE activity levels. Four patients showed GALK hyperactivity. CONCLUSION: GALE deficiency provided the highest number. After lactose-free diet, galactose and galactose-1-phosphate were normaly maintained. Neonatal screening on galactosemia is essential for preventing life-threatening symptoms and an accurate diagnosis is needed for finding out the type of galactosemia which is important for prognosis.

Galactosemia: diagnóstico de 5 casos con deficiencia de transferasa

Se presenta el estudio bioquímico realizado en el Centro Nacional de Genética Médica, a 5 niños, remitidos por sospecha clínica de padecer un error innato del metabolismo de los carbohidratos. Se les realizó la cromatografía en capa fina para la detección de estas sustancias en orina, y se halló una banda al nivel de galactosa. Posteriormente se procedió a la cuantificación del metabolito en sangre, y se detectó a éste elevado en ella. El diagnóstico final consistió en comprobar la deficiencia de la enzima galactosa-1-fosfato uridiltransferasa eritrocitaria, por el método espectrofotométrico; se comprobó también el carácter de portadores del gen deficiente, en los padres de los 5 niños.

The biochemical study of 5 children who were referred to the National Center of Medical Genetics because they were clinically suspected of suffering from an inborn error of the carbohydrate metabolism is presented. Thin layer chromatography was carried out to detect these substances in urine and a band was found at the galactose level. A high level of metabolites in blood was found on quantifying them. The final diagnosis consited in demonstrating the deficiency of erythrocytic galactose-1-phosphate uridyltransferase by the spectrophotometric method. The character of carriers of the deficient gene was also proved among the parents of the 5 children.

Um método simples e rápido para a quantificação de galactose em soro e urina / A simple and rapid method for the measurement of galactose in serum and urine

A galactose presente na circulação ou excretada na urina tem interesse clínico em duas situações: 1) confirmação do diagnóstico ou acompanhamento de pacientes galactosêmicos; 2) em teste de tolerância à lactose, no qual a interpretação é feita rotineiramente de forma indireta pela avaliação da glicemia. Na há disponível no mercado nacional “kit” comercial para a dosagem da galactose em líquidos biológicos. Neste trabalho, descreve-se um método rápido e simples para medida da galactose em soro ou urina.