Classical galactosemia is associated with a severe deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). Affected infants present soon after birth.
Genetic locus: GALT gene (short arm of chromosome 9 at p13)
Galactose is present in:
(1) human and cow milk
(2) fruits and vegetables
Most affected patients present within a few weeks of birth with a life-threatening illness featuring:
(1) poor feeding
(2) poor weight gain, weight loss or failure to thrive
Additional findings include:
(1) hepatomegaly with jaundice
(5) renal tubular disease with metabolic acidosis, galactosuria, glycosuria, albuminuria and aminoaciduria
(6) hemolytic anemia
Late complications include:
(1) impaired cognitive development
(2) delayed but eventually normal growth
(3) ovarian failure in females (hypergonadotropic hypogonadism)
(4) progressive neurologic disease with ataxia
The patient may be detected if newborn screening for galactosemia is performed.
(1) Beuttler spot test (fluorescent spot test measuring NADPH formation, which is very low in classical galactosemia so the test is negative)
(2) consumption of UDP-Glc (not consumed in classical galactosemia)
(3) laboratory analysis for Q188R mutation (most common but not the only mutation)
(4) measurement of plasma Gal-1-P (very high in classical galactosemia)
False negatives on screening tests may occur if the patient has been transfused within the previous 4 months.
A galactose-free diet results in clinical improvement but long term complications still occur despite good adherence to the diet.
To read more or access our algorithms and calculators, please log in or register.