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Galactosemia LB
- 2. Introduction Galactose is converted to glucose to be metabolized. Generally speaking 3 enzymes take part in this process: GALT(galactose-1-phosphate-uridylyltransferase) GALK(galactokinase) GALE(UDP-Gal epimerase) Galactosemia is a hereditary disease caused by lack of a liver enzyme/s required to digest galactose. This shouldn’t be confused with Lactose intolerance which only results in the inability to break down lactose due to Lactase deficiency.
- 5. History Galactosemia was first discovered in 1908 by the physician Von Ruess. Publication entitled, "Sugar Excretion in Infancy," reported on a breast-fed infant with failure to thrive, enlargement of the liver and spleen, and "galactosuria".
- 6. Cont…. In 1917, Goppert reported an infant with poor growth, lactose exposure, and hypergalactosuria The first comprehensive description of the variant form of hereditary galactosemia was in 1935 by Mason and Turner of an African-American infant. It was also the first report of a patient with any form of galactosemia due to GALT deficiency in the American literature. This patient had not been placed on a lactose-restricted diet until 10 months of age.
- 7. Aetiology Galactosemia is an autosomal recessive disorder, meaning the allele must be found in a homozygous form for it to be expressed. Therefore it is usually characterized by: does not usually affect the parents, but siblings may show the disease In many cases, enzyme proteins are affected by the mutation. recurrence risk is 25% for each birth(If parents are hetrozygote) In heterozygotes, equal amounts of normal and defective enzyme are synthesized. ("margin of safety")
- 9. Types and Pathophysiology There are 3 types based on which enzyme is deactivated: Type I (Classic)-(G/G) Both copies of GALT gene(p-arm of chrom 9) are deleterious, no GALT activity Most common and severe Build up of galactose, Gal-1-P, galacitol, galactonate Mostly inherited, with both parents being carriers May be lethal if untreated Lethargy, FTT, liver damage, cataract(tonicity),speech difficulties, intellectual disability, sepsis and shock.
- 10. Gene Symbol Activity level Normal N 100% Galactosemia - non- functioning G 0% Duarte - partially functioning D 50% Los Angeles - above normal functioning gene LA 125%
- 13. Cont… Type II Deleterious mutation in the GALK1 gene(q-arm of chrom 17) Total loss of GALK activity Lower levels of Gal-1-P Presence of Galactosuria Fewer medical problems are seen Some infants develop cataracts
- 14. Cont…. Type III Deleterious mutation of the GALE gene(p-arm of chrom 1) leads to partial loss of the enzymatic activity of GALE The signs and symptoms of galactosemia type III vary from mild to severe and can include cataracts, delayed growth and development, intellectual disability, liver disease, and kidney problems.
- 16. Epidemiology Studies show: Classic galactosemia occurs in 1 in 30,000 to 60,000 newborns Galactosemia type II and type III are less common Type II probably affects fewer than 1 in 100,000 newborns Type III appears to be very rare. 1 in 7,500 births - some form of galactosemia It is estimated that 1 in every 40 people may be a carrier The Duarte variant is found in 1 in 20 persons.
- 17. Symptoms Can manifest in the first few days of life if there is consumption of galactose Symptoms are: Convulsions Irritability Lethargy FTT Jaundice Vomiting Poor feeding
- 18. Exams and Tests These include: Blood culture for bacterial infections (E.coli sepsis) Enzyme activity in red blood cells Ketones in urine Prenatal diagnosis by directly measuring the enzyme galactose-1- phosphate uridylyl transferase "Reducing substances" in the infant's urine, and normal or low blood sugar while the infant is being fed breast milk or a formula containing lactose
- 19. Prognosis People who are diagnosed early and strictly avoid milk products can live a relatively normal life. However, mild mental impairment may develop, even in people who avoid galactose.
- 20. Treatment and prevention People with this condition must avoid all milk, dairy products, and other foods that contain galactose, for life. Instead infants can be fed: Soy formula Another lactose-free formula Meat-based formula or Nutramigen (a protein hydrolysate formula)
- 21. Cont…. helpful for an individual to know their family history Genetic counseling must be given to couples who have a family history of galactosemia If the newborn shows possible galactosemia , they must prevent the newborn from consuming galactose-laden products