Galactosemia – Definition, Causes, and Prevention.

Definition

Galactosemia is a rare, hereditary disorder of carbohydrate metabolism that affects the body’s ability to convert galactose (a sugar contained in milk, including human mother’s milk) to glucose (a different type of sugar). The disorder is caused by a deficiency of an enzyme galactose-1-phosphate uridyl transferase (GALT) which is vital to this process. Early diagnosis and treatment with a lactose-free diet are absolutely essential to avoid profound intellectual disability, liver failure and death in the newborn period.

It is inherited as an autosomal recessive genetic condition. Classic galactosemia and clinical variant galactosemia can both result in life-threatening health problems unless treatment is started shortly after birth. A biochemical variant form of galactosemia termed Duarte is not thought to cause clinical disease.

History of Galactosemia

Galactosemia was first “discovered” in 1908. Von Ruess, in a 1908 publication entitled, “Sugar Excretion in Infancy,” reported on a breastfed infant with failure to thrive, enlargement of the liver and spleen, and “galactosuria”.

This infant ceased to excrete galactose through the urine when milk products were removed from the diet. The infant, however, later died because of other complications (the baby had been given tea laced with cognac as treatment as well). An autopsy revealed cirrhosis of the liver, which they thought was due to the infant’s alcohol ingestion. Though confirmation of the diagnosis was not possible at that time, it has been generally accepted that Von Ruess was the first to report on a patient with galactosemia.

By 1917, “galactosuria” was a broadly recognized inherited disorder and was treated by removal of milk products from the diet.

Epidemiology

Galactosemia is an inherited autosomal recessive disorder that occurs in approximately 1 in 30,000 births. The incidence of the Duarte variant of the classic form of galactosemia is estimated at 1 in 16,000 births. It can occur in all ethnic groups; however, some mutations of the genes can cause a less severe form of the disease and is more commonly seen in individuals of African and Asian descents.

Types

Galactosemia type I, also referred to as classic galactosemia, is the most threatening of all and infants suffering from this condition may even develop life-threatening complications within just a few days of birth unless the infant is put on a low-galactose diet. Affected babies will display a whole range of worrying symptoms and will also most likely have delayed development problems as they grow. One risk that is common to all three types of galactosemia is the risk of developing cataracts of the eye.

Galactosemia type II is a lot less problematic, with fewer and less severe symptoms and it also poses a lower risk of long-term complications. Cataract is the only major long-term risk.

Galactosemia type III can cause symptoms that vary greatly in severity and affected infants may experience developmental problems, delayed growth, and other complications.

Risk factors

• Galactosemia is inherited; the only known risk factor is a family history of the disorder. Galactosemia is inherited as an autosomal recessive trait. Individuals have two copies of most genes, one inherited from the father and one from the mother.
• To inherit a recessive genetic disorder, an individual must receive two copies of the defective gene for the disease to appear.
• People who have only one mutated gene are called “carriers.” If only one parent is a carrier, none of the children will have galactosemia, but each child will have a 50% chance of being a carrier; if both parents are carriers, then each child has a 50% chance of being a carrier, a 25% chance of not inheriting either mutated gene, or a 25% chance of having galactosemia.

Causes of Galactosemia

• Galactosemia is an inherited condition that is caused by mutations in certain genes. It isn’t horribly common and there is a 25% chance of a baby being born with the condition if both parents carry the mutated genes.
• There are three genes responsible and these include the GALE, GALK1, and GALT genes. These genes contain the code or set of instructions for the production of enzymes that are needed to process and break down galactose in the body.
• In a healthy child, these enzymes would break down galactose into glucose and other simple sugars that can be utilized by the body as energy.
• While abnormalities in the GALT gene are responsible for classic galactosemia or galactosemia type I, GALK1 mutations cause galactosemia type II and GALE mutations cause galactosemia type III.

Symptoms

Infants with galactosemia may develop symptoms in the first days of life if they consume milk or milk powder containing lactose. These symptoms may be caused by severe blood infection with the bacterium E-coli and can be:

• Convulsions
• Irritability
• Lethargy
• Child’s refusal to eat milk
• An insignificant increase in weight
• Jaundice
• Vomiting
• Aminoaciduria
• Hepatomegaly
• Ascites
• Hypoglycemia

Children with galactosemia are often given a galactosemia diet at birth, but there is still a risk of complication long-terms.

• An enlarged liver
• Kidney failure
• Cataracts in the eyes
• Brain damage
• Difficulty with speech and language
• Fine and gross motor skill delays
• Learning disabilities
• Ovarian failure may occur in girls

Symptoms of galactosemia

Complications of Galactosemia

These complications can develop:

• Cataracts
• Cirrhosis of the liver
• Delayed speech development
• Irregular menstrual periods, reduced function of ovaries leading to ovarian failure
• Mental disability
• Severe infection with bacteria ( Coli sepsis)
• Tremors (shaking) and uncontrollable motor functions
• Death (if there is galactose in the diet)

Diagnosis and test

A diagnosis of Galactosemia would involve:

• Physical exam with evaluation of medical history; neonates are usually screened for this disorder if the physician suspects the same
• Urine and blood exam – blood sugar and plasma, amino acid analysis
• Blood culture test, to detect any infection (due to bacteria)
• Genetic tests and analysis for mutations, in order to determine the exact type of the condition
• Prenatal exams, in order to measure certain enzymes

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

Doctors, while diagnosing this condition, usually look for signs like:

• Enlarged liver (hepatomegaly)
• Amino acids in the blood plasma and/or urine (aminoaciduria)
• Presence of abdominal fluids (ascites)
• Low blood sugar (Hypoglycemia)

Treatment and medications

Currently, there is no drug or medication that could treat galactosemia. Treatment requires a strict diet restriction of lactose/galactose. People with this condition must avoid all milk, products that contain milk (including dry milk), and other foods that contain galactose, for life. Read product labels to make sure you or your child with the condition are not eating foods that contain galactose.

Parents of an infant diagnosed with galactosemia need to use a formula that does not contain galactose. Infants can be fed:

• Soy formula
• Another lactose-free formula
• Meat-based formula or Nutramigen (a protein hydrolysate formula)
• Calcium supplements are recommended

Even after switching to non-galactose formula, your child may still have sepsis if they have ingested galactose food before. The antibiotic is usually used to prevent sepsis in children.

A person with this condition can never able to digest food with galactose. However, with care and continuing medical advances, most children with galactosemia can now live normal lives

Prevention of Galactosemia

• Galactosemia, like other genetic disorders, cannot be prevented but there are things that parents can do if they have a family history of the disease.
• It would be a good idea for couples to consult genetic counselors to determine if they are carriers and if there is any risk to the child.
• Genetic counseling is required for other family members if Galactosemia has been diagnosed. In many states, newborns are screened for Galactosemia. If you reside in any of these states and the condition is suspected in your child, stop giving him/her milk products.

Avoid milk products