• Milk sugar consists of lactose, glucose and galactose.
• Galactose is used both as an energy source and for the synthesis of galactose-containing cell components such as glycoprotein, glycolipid and mucopolysaccharide.
• A significant part of galactose turns into glucose as a result of enzymatic reactions and provides energy.
• The most important organ in which these reactions take place is the liver.
Galactokinase Deficiency
• The only finding in this enzyme deficiency is cataract.
• Galactose transforms into galactitol with the effect of aldose-reductase enzyme in the lens and cataract occurs. Another very rare complication is pseudotumor cerebri, which develops with the osmotic effect of increased galactitol in the brain.
Classic Galactosemia
• Deficiency of galactose-1-phosphate uridyl transferase (G-1-PUT) enzyme is the most common disease of galactose metabolism.
• Galactose cannot be metabolized beyond galactose-1-phosphate and accumulates in tissues as phosphate esters (toxic to liver, kidney and brain).
• Toxic effect on the lens (cataract) is due to osmotic swelling caused by the accumulation of galactitol.
• The baby is born normally, symptoms appear 3-4 days after starting to feed with milk. Vomiting, diarrhea, jaundice, feeding difficulties, inability to gain weight, hepatomegaly, ascites, cataracts, irritability, hypoglycemic convulsions, mental retardation are the main findings.
• Increased intracranial pressure and cerebral edema may be the first signs. There is often lethargy and marked hypotonia.
• Liver, kidney and brain damage is irreversible in undiagnosed and untreated patients. Anemia and purpura may occur due to hemolysis and deficiency of coagulation factors.
• E.coli sepsis can be seen.
• It causes Fanconi syndrome due to accumulation in kidney tubule cells.
• It is a metabolic disease that causes infertility. Hypergonadotropic hypogonadism (ovarian failure) is seen in 80% of girls.
Laboratory Findings
• Since galactose is a reducing sugar, reducing agent can be detected with Fehling, Benedict solutions and klinitest tablets. The reducing agent is identified by sugar chromatography.
• Measurement of galactose-1-phosphate in erythrocytes is useful in diagnosis and monitoring.
• Enzyme defect can be demonstrated in erythrocytes (Beutler test).
• Antenatal diagnosis can be provided by detecting transferase enzyme activity in amnion cell culture.
• Liver function tests are impaired. Hypoglycemia, clotting factors decreased.
• Hyperchloremic metabolic acidosis and albuminuria are seen.
• Proteinuria, aminoaciduria and glucosuria may be seen due to kidney damage.
Treatment
• It is the removal of galactose from the diet. Vomiting, diarrhea, jaundice, proteinuria, aminoaciduria disappear in a few days with a lactose-free diet. Damages to the liver, brain and eyes are partially regressed. Early diagnosis can prevent the development of cataracts and cirrhosis. A galactose-free diet is given until after puberty. Despite successful diet therapy, some patients develop ataxia, learning difficulties, growth retardation, and in girls, amenorrhea due to hypergonadotropic hypogonadism. This is likely due to accumulation of galactitol, UDP-galactose deficiency or endogenous galactose formation.
Cataract + Prolonged Jaundice +Hypoglycemia = Galactosemia
Epimerase Deficiency
• Enzyme deficiency in erythrocyte is asymptomatic.
• Cases with generalized epimerase deficiency present findings like classical galactosemia. In addition, hypotonia and nervous deafness are observed. Gal-1 phosphate levels are high, but transferase enzyme level is normal.
• Since they cannot make galactose from glucose, a diet low in galactose is recommended, not a galactose-free diet. Because galactose is the building block of proteins in the brain.