Galactosemia
Patient Information
Characteristics
Background and History
Galactosemia is the most serious of a group of disorders with an enzyme defect that leads to inability to breakdown and use the sugar galactose. At least two other similar but milder forms have been found.
Clinical Correlations
The classical signs appear early in infancy and are: cataracts, failure to thrive, and enlargement of the liver. Jaundice is often present and such infants may suffer seizures and feed poorly. Neonates are especially vulnerable to serious and sometimes fatal bacterial infections, especially from E. coli. Some infants have a bleeding disorder as well. It is of vital importance that restrictive diets, low in galactose and lactose (IsomilR or ProsobeeR) be implemented within a few days of birth to prevent the onset of major symptoms and signs.
Unfortunately, the outcome in older individuals can still be disappointing even with strict dietary restrictions. Speech difficulties, mental and muscle problems, failure of the ovaries, and difficulties with balance can occur in some, but not all, older individuals with galactosemia.
Genetics
Inheritance
This is an autosomal recessive disorder that requires the presence of two mutations, one inherited from each normal parent.
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
The combination of an enlarged liver, cataracts, and failure to thrive should suggest the diagnosis to pediatricians and ophthalmologists. Commercial diets, if instituted in the first 3-10 days can prevent many of the early signs of galactosemia but some patients have long term mental and neurological problems. Cataract surgery is often unnecessary with early initiation of the proper dietary restrictions.
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