Symptomatic Effect of Galactosemia Deficiencis
1. Classical Galactosemia
a. cataract formation
b. mental retardation
c. liver cirrhosis
e. impaired renal tubular transport of amino acids
2. Galactokinase Deficiency
b. no mental retardation
c. no neonatal symptoms
3. UDPG-4-epimerase Deficiency
b. usually in RBC
A. Classic galactosemia (Incidence- 1/60,000) refers to the complete deficiency of the GALT enzyme. There are numerous variants where GALT activity is impaired, but not absent.
Symptoms appear early in the neonate as the average newborn normally receives up to 20% caloric intake as lactose. Without the GALT enzyme, the infant is unable to metabolize galactose-1-phosphate, and the resulting accumulation leads to injury to the parenchymal cells of the kidney, liver, and brain. The injury can begin prenatally in the affected fetus via transplacental galactose from the diet of the heterozygous mother or by endogenous production of galactose in the fetus. Because of this endogenous production of galactose, dietary restriction alone may not be sufficient to prevent the adverse outcomes related with this disease.
Clinical Symptoms include: Jaundice (74%), Vomiting (47%), Hepatomegaly (43%), Failure to thrive (29%), Lethargy (16%), Sepsis (10%)- E.coli is the principle cause of early mortality B. Galactosemia II is caused by defects in both copies of the gene that codes for an enzyme called galactokinase (GALK). The frequency of occurrence of galactosemia II is about one in 100,000-155,000 births.
Galactosemia II is less harmful than galactosemia I. Babies born with galactosemia II will develop cataracts at an early age unless they are given a galactose-free diet. They do not generally suffer from liver damage or neurologic disturbances. C. Galactosemia III is caused by defects in the gene that codes for an enzyme called uridyl diphosphogalactose-4-epimerase (GALE). This form of...
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