Galactose Epimerase Deficiency
Patient Information
Characteristics
Background and History
This is one of three rare disorders in which the breakdown of a sugar molecule, galactose, is defective resulting in disease. Clinical symptoms in this disorder, however, are highly variable.
Clinical Correlations
Some patients with this form of galactosemia have few symptoms and develop normally. Others, however, can have severe disease resulting in cataracts, liver disease, mental retardation and a general failure to thrive. Vomiting, jaundice, and seizures may be seen in the neonatal period. Such infants can be especially susceptible to bacterial infections, especially from E. coli.
Genetics
Inheritance
This is an autosomal recessive disorder which requires the presence of two mutations for the disease to appear. Each normal parent, called a carrier, contributes one mutation and they have a risk of 25% during each pregnancy to have another affected child. The mutant gene, called GALE, does not make normal levels of the enzyme product needed to metabolize galactose.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
Early diagnosis is extremely important for treatment with a diet low in content of galactose is therapeutic. Usually the diagnosis is made shortly after birth when red blood cell analysis reveals a low level of the specific enzyme.
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